Bioethanol Production from Various Lignocellulosic Materials by Encapsulated Saccharomyces cerevisiae NCIM 3095

Bioethanol has a greater promise for environmental safety and energy security than fossil fuels. The alternate source required to meet the fuel's requirements can be provided by bioethanol. Untapped sugar-rich sources, like cellulose-rich household wastes, industrial wastes, and agricultural wastes, can all be used to make bioethanol at a minimal cost. The study's objective was to determine whether saccharomyces cerevisiae cells from the encapsulated NCIM 3095 strain of Saccharomyces cerevisiae could be used to make low-cost ethanol from a variety of lignocellulosic wastes, including newspaper, banana leaves, gram straw, soybean straw, and cow dung. To reduce bacterial contamination and serve as an external growth stimulator, benzathine penicillin G and ammonium sulfate were added to each sample broth containing calcium alginate-encapsulated yeast cells. The samples were fermented for ten days. The ethanol content was evaluated every three days. The largest yield of bioethanol was produced by soybean straw (10.0%), while the lowest was by cow dung (4.0%).

A simple method for the determination of bioethanol from lignocellulosic materials using gas chromatography-flame ionisation detector (GC-FID)

Aims@#The utilisation of lignocellulosic biomass for bioethanol production reduces the dependency on fossil fuels as a source of energy and emission of greenhouse gas (GHG). However, studies in this emerging field are hampered by the cost of ethanol quantification methods. Due to the volatile nature of ethanol, the method for the quantification of bioethanol production should be reproducible and rapid to avoid any evaporation loss to the surroundings. Therefore, this study aimed to develop a simple, rapid and precise bioethanol quantification method using a gas chromatographyflame ionisation detector (GC-FID) without having to go through distillation process for ethanol purification.@*Methodology and results@#The bioethanol was produced via consolidated bioprocessing (CBP) using Trichoderma asperellum B1581 and paddy straw. The peak corresponding to ethanol was obtained at 2.347 min with a peak area of 189.66, equating to 0.159% (v/v) or 1.25 g/L ethanol. A comparison between the quantity of ethanol detected by GC-FID and spectrophotometric analysis (340 nm) showed no significant difference (p>0.05) in the amount of ethanol detected by GC analysis, thus validating the accuracy of the GC method.@*Conclusion, significance and impact of study@#This work presents a simple, precise and reliable method to determine the amount of bioethanol in the sample using a GC-FID. Currently, there are many GC-FID methods available for the determination of ethanol/alcohol in a human blood samples or in beverages but not in bioethanol samples. Thus, this method was developed to facilitate the determination of bioethanol in the samples produced from lignocellulosic materials.

Obtención de bioproductos a partir de residuos del beneficio húmedo del café (pulpa) / Obtaining Bioproducts from Residues of the Wet Benefit of Coffee (Pulp)

RESUMEN Este trabajo presenta los resultados obtenidos a escala de laboratorio para el aprovechamiento de la pulpa de café (residuos) en el proceso de beneficio húmedo aplicando el concepto de biorrefinería. Los resultados mostraron que es posible tratar este residuo mediante procesos fermentativos y obtener bioetanol separado por medio de la destilación simple con un contenido de alcohol entre 3,85 % al 6,90 % por cada 250 ml de biomasa tratada en condiciones ambientales. Se observó en todos los ensayos que una variable importante es el tiempo de fermentación y la estructura inicial del residuo ya que esto influye sobre el rendimiento obtenido en términos del bioalcohol producido. Este trabajo forma parte de un estudio preliminar para la implementación del concepto de biorrefinería a los residuos generados en el beneficio húmedo del café. La búsqueda de alternativas que permitan el aprovechamiento de los residuos del café constituye una problemática actual. Estos residuos al no ser tratados, por lo general son vertidos a las fuentes hídricas y en ocasiones utilizados como enmiendas agrícolas en los cultivos, lo cual puede causar graves problemas de contaminación. Por este motivo es necesario realizar investigaciones en este campo que permitan su tratamiento o aprovechamiento integral.

ABSTRACT This work presents the results obtained at a laboratory scale for the use of coffee pulp (residues) in the wet milling process applying the concept of biorefinery. The results showed that it is possible to treat this residue through fermentative processes and obtain bioethanol through simple distillation with an alcohol content between 3.85% to 6.90% for each 250ml of biomass with a solid-liquid ratio of 4 to 1 to environmental conditions. It was observed in all the tests that the fermentation time and the initial structure of the residue are important variables since they influence the yield obtained in terms of produced alcohol. This work is part of a preliminary study for the implementation of the biorefinery concept to the residues generated in the wet coffee mill. The search of alternatives that allow the use of coffee residues is a current problem. These residues, when not treated, are generally dumped into water sources and sometimes used as agricultural amendments in crops, which can cause serious contamination problems. For this reason, it is necessary to carry out research in this field for its treatment or comprehensive use.

Bioethanol production from urban cellulosic waste employing Alcaligenes faecalis HI-1 isolated from gut of termite Heterotermes indicola

This study assessed the potential of termite gut inhabiting bacteria towards bioconversion of cellulosic waste into biofuel. Total seven bacterial isolates from the gut of Heterotermes indicola were isolated. Among all the isolates, HI-1 produced the largest zone upon primary screening. Untreated paper had more cellulose content (73.03%) than acid (0.5%) treated paper that was used as a lignocellulosic substrate for saccharification. Among all the isolates tested, glucose yield (1.08mg/mL) was high for HI-1 isolate. Several factors were considered for optimizing augmented glucose yield (8.57mg/mL) and growth (8.07×108cfu/mL), such as temperature 37°C, pH 4.5, 5% (w/v) substrate concentration, 6 % bacterial inoculum size, agitation 150 rpm with PEG 0.25 % and Ca2+ ions 0.002 g/L. Overall 8-fold increase in glucose yield was achieved. Enzyme activity of HI-1 showed higher endoglucanase 0.29 ± 0.01 (U/mL/min) and exoglucanase 0.15±0.01 (U/mL/min) activity under optimum conditions, mentioned above. temperature 37°C, pH 4.5, substrate concentration 5%, inoculum size 6%, surfactants PEG 0.01%, ions Ca2+(0.002g/L) and agitation (120 rpm). Simultaneous saccharification and fermentation (SSF) of hydrolyzed office paper yielded 5.43mg/mL bioethanol. According to 16S rRNA sequence homology, the bacterial isolate H1 was identified as Alcaligenes faecalis. Bioethanol production from office paper untreated waste proved an effective strategy. Bacteria having natural tendency towards cellulosic waste consumption are promising for bioconversion of cellulosic waste to valuable products.

Enhance of Cellulase Production and Biomass Degradation by Transformation of the Trichoderma reesei RUT-C30∆ zface1 Strain

Abstract The second-generation bioethanol employs lignocellulosic materials degraded by microbial cellulases in their production. The fungus Trichoderma reesei is one of the main microorganisms producing cellulases, and its genetic modification can lead to the optimization in obtaining hydrolytic enzymes. This work carried out the deletion of the sequence that encodes the zinc finger motif of the transcription factor ACE1 (cellulase expression repressor I) of the fungus T. reesei RUT-C30. The transformation of the RUT-C30 lineage was confirmed by amplification of the 989 bp fragment relative to the selection marker, and by the absence of the zinc finger region amplification in mutants, named T. reesei RUT-C30Δzface1. The production of cellulases by mutants was compared to RUT-C30 and measured with substrates carboxymethylcellulose (CMC), microcrystalline cellulose (Avicel®) and Whatman filter paper (PF). The results demonstrated that RUT-C30Δzface1 has cellulolytic activity increased 3.2-fold in Avicel and 2.1-fold in CMC and PF. The mutants presented 1.4-fold higher sugar released in the hydrolysis of the biomass assays. These results suggest that the partial deletion of ace1 gene is an important strategy in achieving bioethanol production on an industrial scale at a competitive price in the fuel market.

Effective diffusion coefficients and bioconversion rates of inhibitory compounds in flocs of Saccharomyces cerevisiae

Background: Fermentation strategies for bioethanol production that use flocculating Saccharomyces cerevisiae yeast need to account for the mechanism by which inhibitory compounds, generated in the hydrolysis of lignocellulosic materials, are tolerated and detoxified by a yeast floc. Results: Diffusion coefficients and first-order kinetic bioconversion rate coefficients were measured for three fermentation inhibitory compounds (furfural, hydroxymethylfurfural, and vanillin) in self-aggregated flocs of S. cerevisiae NRRL Y-265. Thièle-type moduli and internal effectiveness factors were obtained by simulating a simple steady-state spherical floc model. Conclusions: The obtained values for the Thiéle moduli and internal effectiveness factors showed that the bioconversion rate of the inhibitory compounds is the dominant phenomenon over mass transfer inside the flocs.

Assessment of wasteland derived biomass for bioethanol production

Background: The bioethanol produced from biomass is a promising alternative fuel. The lignocellulose from marginal areas or wasteland could be a promising raw material for bioethanol production because it is present in large quantities, is cheap, renewable and has favorable environmental properties. Despite these advantages, lignocellulosic biomass is much more difficult to process than cereal grains, due to the need for intensive pretreatment and relatively large amounts of cellulases for efficient hydrolysis. Therefore, there is a need to develop an efficient and cost-effective method for the degradation and fermentation of lignocellulosic biomass to ethanol. Results: The usefulness of lignocellulosic biomass from wasteland for the production of bioethanol using pretreatment with the aid of ionic liquids of 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium chloride was evaluated in this study. The pretreatment process, enzymatic hydrolysis and alcoholic fermentation lasted a total of 10 d. The largest amounts of bioethanol were obtained from biomass originating from agricultural wasteland, in which the dominant plant was fireweed (Chamaenerion angustifolium) and from the field where the common broom (Cytisus scoparius) was the dominant. Conclusions: The plants such as fireweed, common broom, hay and goldenrod may be useful for the production of liquid biofuels and it would be necessary in the further stage of research to establish and optimize the conditions for the technology of ethyl alcohol producing from these plant species. Enzymatic hydrolysis of biomass from agricultural wastelands results in a large increase in fermentable sugars, comparable to the enzymatic hydrolysis of rye, wheat, rice or maize straw.

Adaptive evolution and selection of stress-resistant Saccharomyces cerevisiae for very high-gravity bioethanol fermentation

Background: In industrial yeasts, selection and breeding for resistance to multiple stresses is a focus of current research. The objective of this study was to investigate the tolerance to multiple stresses of Saccharomyces cerevisiae obtained through an adaptive laboratory evolution strategy involving a repeated liquid nitrogen freeze­thaw process coupled with multi-stress shock selection. We also assessed the related resistance mechanisms and very high-gravity (VHG) bioethanol production of this strain. Results: Elite S. cerevisiae strain YF10-5, exhibiting improved VHG fermentation capacity and stress resistance to osmotic pressure and ethanol, was isolated following ten consecutive rounds of liquid nitrogen freeze­thaw treatment followed by plate screening under osmotic and ethanol stress. The ethanol yield of YF10-5 was 16% higher than that of the parent strain during 35% (w/v) glucose fermentation. Furthermore, there was upregulation of three genes (HSP26, HSP30, and HSP104) encoding heat-shock proteins involved in the stress response, one gene (TPS1) involved in the synthesis of trehalose, and three genes (ADH1, HXK1, and PFK1) involved in ethanol metabolism and intracellular trehalose accumulation in YF10-5 yeast cells, indicating increased stress tolerance and fermentative capacity. YF10-5 also showed excellent fermentation performance during the simultaneous saccharification and fermentation of VHG sweet potato mash, producing 13.40% (w/ v) ethanol, which corresponded to 93.95% of the theoretical ethanol yield. Conclusions: A multiple-stress-tolerant yeast clone was obtained using adaptive evolution by a freeze­thaw method coupled with stress shock selection. The selected robust yeast strain exhibits potential for bioethanol production through VHG fermentation.

Feasibilitiy Study of Bioethanol Production: A Case of Spent Mushroom and Waste Paper as Potential Substrate

Aims: The aim of the present study is to produce ethanol from waste paper and spent mushroom using Saccharomyces cerevisiae as enzymes for the fermentation process. Study Design: Waste paper and spent mushroom samples were subjected to fermentation and hydrolysis by Aspergilus niger and Saccharomyces cerevisiae to produce bioethanol. Place and Duration of Study: This study was carried out in the Environmental Microbiology Laboratory, University of Port Harcourt, Nigeria, between May and October 2017. Methodology: Waste paper and spent mushrooms samples were hydrolyzed by Aspergillus niger, and the hydrolysate from each set up subjected to fermentation by Saccharomyces cerevisiae. Ethanol was extracted by fractional distillation, and qualitatively determined by Gas Chromatography with Mass Spectrometry. Results: After 8 days of fermentation, there was decrease in glucose content in waste paper hydrolysate ranging from (0.51-0.1 mg/l), and spent mushroom substrate (0.3-0.07 mg/l). Upon extraction of the bioethanol, the highest yield was recorded for waste paper hydrolysate which after characterization with GC-MS ethanol concentration was 28.01 mg/l, followed by spent mushroom hydrolysate 26.8 mg/l. Conclusion: This study revealed that bioethanol can be obtained from fermentation of waste paper using Saccharomyces cerevisiae and ethanol can be obtained after the paper has been used in growing edible mushroom; if adopted, this could be a way to achieving environmental sustainability.

Efecto de antibióticos y un antimicrobiano sobre el control de bacterias acido lácticas en la fermentación alcohólica / Effect of antibiotics and an antimicrobial on the control of lactic acid bacteria in alcoholic fermentation

RESUMEN El propósito de esta investigación fue evaluar el efecto de antibióticos y un antimicrobiano para el control de bacterias ácido lácticas (BAL) en etapa fermentativa de tres ingenios (A, B y C) productores de alcohol en el Valle del Cauca (Colombia). Se establecieron dos ensayos de fermentación a escala de laboratorio por separado, tratados con cuatro antibióticos (8, 15 y 30 ppm), dos cocteles (4, 8 y 15 ppm) y un antimicrobiano (15 y 30 ppm); en el primero se cuantificó la producción de ácido láctico (AL), la población y viabilidad de la levadura, y en el segundo se determinó el crecimiento de BAL. En el primer ensayo, los tratamientos que controlaron los niveles de AL en los ingenios fueron virginiamicina (VIR) 15 ppm, maduramicina (MAD) 15 ppm, penicilina (PEN) 30 ppm y lúpulo (LUP) (30 ppm). Adicionalmente, los tratamientos PEN a 30 ppm, VIR, el coctel estreptomicina-penicilina-virginiamicina-monensina (EPVM) y LUP a 15 ppm no afectaron a la levadura en las condiciones evaluadas. En el ensayo dos, todos los tratamientos lograron controlar BAL, presentando un mayor control a las 24 horas pos-tratamiento en el ingenio A. En el ingenio B, MAD, monensina (MON), los cocteles estreptomicina-penicilina-virginiamicina (EPV) y EPVM, controlaron el crecimiento de BAL durante las primeras 6 horas, mientras que LUP controló la población de BAL a las 24 horas. En el ingenio C, LUP, MON y EPV lograron controlar las BAL en todas las concentraciones, principalmente a las 24 horas. Por tanto, se infiere que VIR en el ingenio A, EPVM en los ingenios B y C y el antimicrobiano LUP en los tres ingenios son eficientes en el control de BAL.

ABSTRACT The objective of this research was to evaluate the effect of antibiotics and an antimicrobial for the control of lactic acid bacteria (LAB) in the fermentative stage of three sugar mills producer (A, B and C), in "Valle del Cauca" (Colombia). Two fermentation assays on laboratory scale separately, treated with four antibiotics (8, 15 and 30 ppm), two cocktails (4, 8 and 15 ppm) and an antimicrobial (15 and 30 ppm) were established. In the first one, lactic acid (LA) production, population and yeast viability were quantified, and in the second the LAB growth was determined. In the first assay, the treatments that controlled LA levels in sugar mills were virginamicin (VIR) 15 ppm, maduramycin (MAD) 15 ppm, penicillin (PEN) 30 ppm and hop (HP) (30 ppm). Additionally, PEN treatments at 30 ppm, VIR, the streptomycin-penicillin-virginiamycin-monensin cocktail (SPVM) and HP at 15 ppm did not affect the yeast under the conditions evaluated. In the second assay, all treatments managed to control of LAB, with greater control at 24 hours in sugar mill A. In sugar mill B, MAD, monensin (MON), streptomycin-penicillin-virginiamycin (SPV) and SPVM cocktails controlled LAB growth during the first 6 hours, while HP controlled LAB population at 24 hours. In sugar mill C, HP, MON and EPV managed to control LAB in all concentrations mainly at 24 hours. Therefore, it is inferred that VIR in sugar mill A, SPVM in sugar mills B and C and HP antimicrobial in the three mills are efficient in LAB control.

Bioethanol Production by Enzymatic Hydrolysis and Fermentation of Cocoyam

Bioethanol, produced by anaerobic fermentation of carbohydrates with microorganism is a liquid fuel used either as energy source or as an additive/enhancer for fossil petrol. This research was carried out to explore the potential of cocoyam starch as an alternative feedstock for bioethanol production. Cocoyam corms and cormels were peeled, dried and milled to flour, the slurries were then mashed with different enzyme cocktails comprising of amylase, glucoamylase and protease enzymes. The saccharified wort obtained was fermented with yeast; Saccharomyces cerevisiae without exogenous nutrient supplementation. Two fermentation processes were employed. Simultaneous Saccharification and Fermentation (SSF) and Separate Hydrolysis and Fermentation (SHF). Glucose liberated during mashing was determined by glucose oxidase method and it was found that enzymatic hydrolysis of cocoyam flour was effective in yielding favourable levels of fermentable glucose up to 86g glucose/100g substrate with batch 1 of enzymes. Ethanol production was measured from the cocoyam mash and it was found that S. cerevisiae produced ethanol levels equating to 398 L/ton which compares favourably with yields from cassava 280 L/ton and corn 420 L/ton. These observations indicated that cocoyam can serve as a very cheap alternative biomass for bioconversion to bioethanol with minimal inputs.

Bioconversion of hemicellulosic materials into ethanol by yeast, Pichia kudriavzevii 2-KLP1, isolated from industrial waste / Bioconversión de materiales hemicelulósicos en etanol por la levadura Pichia kudriavzevii 2-KLP1 aislada de residuos industriales

In the present work, a yeast strain Pichia kudriavzevii was identified on the basis of 18S rDNA, showing maximum growth at 30°C and pH 7.0. Among all the complex polysaccharides used, wheat bran proved to be the best substrate as indicated by the maximum growth of the yeast strain. The yeast isolate was capable of producing xylanase both intra-and extra-cellularly, the dominant form being extracellular. The maximum enzyme activity was determined at pH 5.0 and at 50°C. Na+, Mg2+ and Fe2+ presence caused a substantial increase in enzyme activity while a slight decrease (4.5%) was observed in the presence of Mn2+, Zn2+ and Cu2+. Pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activities were assayed to confirm the presence of the ethanol pathway and PDC activity was much more pronounced (73%) compared to ADH activity (51%). The yeast strain can be employed to utilize hemicellulose containing agroindustrial residues for ethanol production.

En el presente estudio se identificó en aguas residuales de una zona industrial de Pakistán una cepa de la levadura Pichia kudriavzevii sobre la base del 18S ADNr, dicha cepa mostró un crecimiento máximo a 30 °C y a pH 7. Entre todos los sustratos de crecimiento evaluados para esta cepa, que incluyeron residuos industriales y medios definidos, el salvado de trigo demostró ser el mejor en función del crecimiento máximo alcanzado. Este aislado de levadura fue capaz de producir xilanasa intracelular y extracelular, esta última fue la forma predominante. Dicha capacidad enzimàtica mostró ser óptima a un pH de 5 y a 50°C. La presencia de Na+, Mg2+ y Fe2+ causó un incremento sustancial de la actividad enzimática, y hubo un ligero descenso (4,5%) en presencia de Mn2+, Zn2+ y Cu2+. Se evaluaron también las actividades de piruvato descarboxilasa y alcohol deshidrogenasa para confirmar la presencia de la vía del etanol. La actividad de la piruvato descarboxilasa fue mucho más pronunciada (73%) en comparación con la de alcohol deshidrogenasa (51%). Esta cepa de levadura puede emplearse para aprovechar los materiales hemicelulósicos de los residuos agroindustriales en la producción de etanol.

Production of Bioethanol from Sugarcane Bagasse Using Saccharomyces Cerevisiae

Ethanol is an alternative fuel derived from renewable biological resources. It's a good substitute for gasoline in spark ignition engines. In this study, the sugar cane bagasse was chemically pretreated with 1% NaOH at room temperature for 2 hours. Dilute acid H2SO4 and Aspergillus niger was used to hydrolyse the biomass to sucrose. Fermentation of the hydrolysed sample was done using Saccharomyces cerevisiae. The fermented product was purified by distillation process at 78oC, and the fraction was collected, and the ethanol was determined by measuring the specific gravity. The production of ethanol from sugar cane bagasse with Saccharomyces cerevisiae was determined after the inoculation into sample A1, A2 and B1 and B2 and highest ethanol produced were from B1 with 0.090 followed B2 0.074, A2 with 0.069% and D 0.116. The use of Saccharomyces cerevisiae gives a better yield. The result of this study can be of a better application in the large production of biofuel from sugar cane bagasse which is renewable and highly abundant, it is saving costs by recycling of wastes, and it also helps to alleviate environmental problem such as an excessive release of greenhouse gases from combustion of non-renewable fossil fuel. From the chromatograph, when the peaks spectrum wave analysed by mass spectrometer of the three volatile organic compounds, two were common to both samples, A contains the abundance of Acetic acid 22.37%, Ethyl alcohol 13.55% isobutene 64.08%. While that of Sample B contains the abundance Acetic acid 17.43%, Ethyl alcohol 7.12% and Propane 75.4.according to Pasteur this is due to Microbial oxidation of ethanol to acetic acid that decreases metabolic toxicity to the yeast cells. This study has proven the efficiency of Saccharomyces cerevisiae for the production of bioethanol.

Improvement of Delignification, Desilication and Cellulosic Content Availability in Paddy Straw via Physico-chemical Pretreatments

Aim: Paddy straw consists of cellulose and hemicellulose as their plant materials leading to their potential to produce bioethanol through several processes such as pretreatment, enzymatic hydrolysis and ethanol fermentation. Among these processes, pretreatment of paddy straw is particularly important for enzymatic hydrolysis process as they are being limited by the presence of ash and silica content. This study was set to observe the effect of different pretreatments on cellulose, hemicellulose, lignin and ash content of paddy straw. Place and Duration of Study: This study was conducted in Department of Biology, Faculty of Science, Universiti Putra Malaysia, between October 2015 and June 2016. Methodology: Pretreatments comprises the combination of physical (mechanical) and chemical treatments to modify the lignocellulosic structure while reduce lignin and separate silica content in paddy straw fibre. Paddy straw was prepared into three different sizes (2mm, 5mm and 8 mm) for physical treatment. Autoclave, boiled and four different concentrations (0.5%, 1%, 2% and 5% (v/v) and (w/v) respectively) of nitric acid and sodium hydroxide, respectively for chemical treatment were used on paddy straw. Results: Size five millimeter paddy straw showed the highest cellulose content (35.61%) compared to the other sizes and when the paddy pretreated with 2% (w/v) sodium hydroxide (NaOH), the percentage of cellulose content escalated to 72.47%. Pretreatment of 2% (w/v) NaOH have performed the most efficient delignification and desilication process (1.02% lignin; 5.44 ash content); and the performance was supported with SEM images on surface area of the paddy straw with large distortion caused by the treatment. Conclusion: Therefore, a physico-chemical pretreatment of size 5 mm and 2% (w/v) NaOH was found to be the most suitable condition to break the cellulose-lignin complex and make the paddy straw becomes feasible for biofuel production.

Progress in research of pentose transporters and C6/C5 co-metabolic strains in Saccharomyces cerevisiae / 生物工程学报

One of the requirements for increasing the economic profitability on the large-scale production of second-generation ethanol and other bio-chemicals using lignocellulose biomass as raw materials is efficient hexose and pentose utilization. Saccharomyces cerevisiae, the traditional ethanol producer, is an attractive chassis cell due to its robustness towards harsh environmental conditions and inherent advantages. But S. cerevisiae cannot utilize pentose. The precision construction of suitable strains for second-generation bio-ethanol production has been taken for more than three decades based on the principle of metabolic engineering and synthetic biology. The resulting strains have improved significantly co-fermentation of glucose and xylose. Recently, much attentions have been focused on sugar transport, which is one of the limiting but formerly ignored step for ethanol production from both glucose and xylose, to get the desired state that different sugars could efficiently delivered by their individual specific transporters. In this paper, the progress on sugar transporters of S. cerevisiae was reviewed, and the research status of xylose and/or L-arabinose metabolic engineering in S. cerevisiae were also presented.

Isolation of thermotolerant xylose-utilizing yeasts for ethanol and xylitol production

Aims@#The implementation of simultaneous saccharification and co-fermentation (SScF) and consolidated bioprocessing (CBP) is highly anticipated for industrial bioethanol applications. Thus, microorganisms capable of utilizing hexose and pentose sugars, as well as thermotolerant, are considered advantageous for optimum ethanol production.@*Methodology and results@#Thermotolerant yeast strains were isolated from wastewater ponds of ethanol-producing facility as well as empty fruit bunch composting area and screened for xylose- and glucose-fermenting ability. Five out of 24 total isolates were able to grow at 40 ºC and were found positive for ethanol production from xylose. Based on their high efficiency of xylose and glucose utilization, two isolates were chosen for further characterization. They were identified as Kluyveromyces marxianus UniMAP 1-1 and Schwanniomyces etchellsii UniMAP 1-7 based on the D1/D2 region of the large subunit ribosomal DNA. The growth kinetics of each isolate on xylose and glucose at 40 °C were determined. The two isolates were able to ferment xylose to ethanol at a maximum concentration between 0.533  0.415 and 1.243  0.246 g/L with concomitant xylitol production between 9.932  0.303 and 12.933  0.505 g/L. Fermentation of glucose to ethanol was also tested for these isolates and the yields were and 0.361 and 0.118 g/g for UniMAP 1-1 and UniMAP 1-7, respectively.@*Conclusion, significance and impact of study@#The potential of these thermotolerant microbes to be used for xylitol and bioethanol production from lignocelluloses are evident from this study.

Inhibitor tolerance of a recombinant flocculating industrial Saccharomyces cerevisiae strain during glucose and xylose co-fermentation

ABSTRACT Lignocellulose-derived inhibitors have negative effects on the ethanol fermentation capacity of Saccharomyces cerevisiae. In this study, the effects of eight typical inhibitors, including weak acids, furans, and phenols, on glucose and xylose co-fermentation of the recombinant xylose-fermenting flocculating industrial S. cerevisiae strain NAPX37 were evaluated by batch fermentation. Inhibition on glucose fermentation, not that on xylose fermentation, correlated with delayed cell growth. The weak acids and the phenols showed additive effects. The effect of inhibitors on glucose fermentation was as follows (from strongest to weakest): vanillin > phenol > syringaldehyde > 5-HMF > furfural > levulinic acid > acetic acid > formic acid. The effect of inhibitors on xylose fermentation was as follows (from strongest to weakest): phenol > vanillin > syringaldehyde > furfural > 5-HMF > formic acid > levulinic acid > acetic acid. The NAPX37 strain showed substantial tolerance to typical inhibitors and showed good fermentation characteristics, when a medium with inhibitor cocktail or rape straw hydrolysate was used. This research provides important clues for inhibitors tolerance of recombinant industrial xylose-fermenting S. cerevisiae.

Improvement of ethanol production from sweet sorghum juice under batch and fed-batch fermentations: effects of sugar levels, nitrogen supplementation, and feeding regimes

Background: Fermentation process development has been very important for efficient ethanol production. Improvement of ethanol production efficiency from sweet sorghum juice (SSJ) under normal gravity (NG, 160 g/L of sugar), high gravity (HG, 200 and 240 g/L of sugar) and very high gravity (VHG, 280 and 320 g/L of sugar) conditions by nutrient supplementation and alternative feeding regimes (batch and fed-batch systems) was investigated using a highly ethanol-tolerant strain, Saccharomyces cerevisiae NP01. Results: In the batch fermentations without yeast extract, HG fermentation at 200 g/L of sugar showed the highest ethanol concentration (PE, 90.0 g/L) and ethanol productivity (QE, 1.25 g/L·h). With yeast extract supplementation (9 g/L), the ethanol production efficiency increased at all sugar concentrations. The highest PE (112.5 g/L) and QE (1.56 g/L·h) were observed with the VHG fermentation at 280 g/L of sugar. In the fed-batch fermentations, two feeding regimes, i.e., stepwise and continuous feedings, were studied at sugar concentrations of 280 g/L. Continuous feeding gave better results with the highest PE and QE of 112.9 g/L and 2.35 g/L·h, respectively, at a feeding time of 9 h and feeding rate of 40 g sugar/h. Conclusions: In the batch fermentation, nitrogen supplementation resulted in 4 to 32 g/L increases in ethanol production, depending on the initial sugar level in the SSJ. Under the VHG condition, with sufficient nitrogen, the fed-batch fermentation with continuous feeding resulted in a similar PE and increased QP by 51% compared to those in the batch fermentation.

Cyanobacteria cell factories for ethanol photosynthetic production: development and prospect / 生物工程学报

Bioethanol is one of the most promising and representative biofuel products. Photosynthetic production of ethanol using CO₂ and solar energy based on cyanobacteria is of great significance for research and application, due to the potential to reduce CO₂ emission and to provide renewable energy simultaneously. Here we review the history and updated development of cyanobacteria cell factories for ethanol photosynthetic production, the progress and problems in pathway optimization, chassis selection, and metabolic engineering strategies, and finally indicate the future development in this area.

Bioethanol production from coconut husk fiber / A produção de bioetanol a partir de fibra de casca de coco

ABSTRACT: Population growth and the increasing search for healthy foods have led to a major consumption of coconut water and, hence, to an environmental impact caused by the inappropriate disposal of green coconut husks. This lignocellulosic biomass has deserved attention of researchers concerning the seeking of new usages, as, for example, in renewable fuels production technologies. This study examines the potential of green coconut husk fibers as a feedstock for the production of bioethanol. The coconut fibers were pretreated through an alkaline method, hydrolyzed enzymatically and submitted to ethanol fermentation with commercial yeasts of Saccharomyces cerevisiae. Despite the significant loss of cellulose (4.42% in relation to the fiber and 17.9% concerning the original cellulose content), the alkaline pretreatment promoted an efficient solubilization of lignin (80%), turning the coconut fibers into a feasible raw material for 2G ethanol production studies. Enzymatic hydrolysis converted 87% of the sugars and the ethanolic fermentation consumed 81% of the substrate in the hydrolyzate, leading to a sugar to ethanol convertion efficiency of 59.6%. These results points out that green coconut husks are a promising alternative to the production of renewable energy.

RESUMO: O crescimento populacional e a busca por alimentos saudáveis levam a um aumento do consumo da água de coco e, com isso, um impacto ambiental pela maior geração de resíduos, merecendo atenção de pesquisadores para o aproveitamento dessa biomassa, em que uma das tecnologias empregadas é a produção de combustíveis renováveis. Este trabalho avalia a fibra da casca de coco verde pré-tratada com álcali, hidrolisada com enzima e submetida à fermentação etanólica com a levedura comercial Saccharomyces cerevisiae. Apesar da significativa perda em celulose (4,42% em relação à biomassa e 17,9% em relação à celulose presente), o pré-tratamento alcalino apresentou alta solubilização de lignina (80%), tornando-se viável para estudos da produção de etanol 2G. A hidrólise enzimática converteu 87% dos açúcares e a fermentação etanólica consumiu 81% do substrato presente no hidrolisado, gerando uma eficiência na conversão de açúcares em etanol de 59,6%. Tais resultados indicam a casca de coco verde como uma alternativa promissora à produção de energia renovável.