Physiological evaluation of yeast strains under anaerobic conditions using glucose, fructose, or sucrose as the carbon source.

The aim of this study was to evaluate the physiology of 13 yeast strains by assessing their kinetic parameters under anaerobic conditions. They included Saccharomyces cerevisiae CAT-1 and 12 isolated yeasts from different regions in Brazil. The study aimed to enhance understanding of the metabolism of these strains for more effective applications. Measurements included quantification of sugars, ethanol, glycerol, and organic acids. Various kinetic parameters were analyzed, such as specific substrate utilization rate (qS), maximum specific growth rate (µmax), doubling time, biomass yield, product yield, maximum cell concentration, ethanol productivity (PEth), biomass productivity, and CO2 concentration. S. cerevisiae CAT-1 exhibited the highest values in glucose for µmax (0.35 h-1), qS (3.06 h-1), and PEth (0.69 gEth L-1 h-1). Candida parapsilosis Recol 37 did not fully consume the substrate. In fructose, S. cerevisiae CAT-1 stood out with higher values for µmax (0.25 h-1), qS (2.24 h-1), and PEth (0.60 gEth L-1 h-1). Meyerozyma guilliermondii Recol 09 and C. parapsilosis Recol 37 had prolonged fermentation times and residual substrate. In sucrose, only S. cerevisiae CAT-1, S. cerevisiae BB9, and Pichia kudriavzevii Recol 39 consumed all the substrate, displaying higher PEth (0.72, 0.51, and 0.44 gEth L-1 h-1, respectively) compared to other carbon sources.

Metabolic engineering of Kluyveromyces marxianus for biomass-based applications.

Kluyveromyces marxianus ATCC 26,548 was cultivated in aerobic chemostats with [1-13C] and [U-13C] glucose as carbon source under three different growth conditions (0.10, 0.25, and 0.5 h-1) to evaluate metabolic fluxes. Carbon balances closed always within 97-102%. Growth was carbon limited, and the cell yield on glucose was the same. The extracellular side-product formation was very low, totaling 0.0008 C-mol C-mol-1 substrate at 0.5 h-1. The intracellular flux ratios did not show significant variation for metabolic flux analysis from labelling and biomass composition and metabolic flux ratio analysis from labelling. The observed strictly oxidative metabolism and the stability of the metabolism in terms of fluxes even at high growth rates, without triggering out the synthesis of by-products, is an extremely desired condition that underlines the potential of K. marxianus for biotechnological biomass-related applications and the comprehension of the metabolic pools and pathways is an important step to engineering this organism. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-022-03324-x.

UV-B Irradiation Effect on Microalgae Performance in the Remediation of Effluent Derived from the Cigarette Butt Cleaning Process.

In this study, the potential of ultraviolet B (UV-B) radiation to alleviate the effects of pollutants in cigarette butt wastewater (CBW) was investigated using different Chlorella sorokiniana strains (F4, R1 and LG1). Microalgae were treated with UV-B (1.7 W m-2) for 3 days prior to their exposure to CBW and then incubated for 4 days in the absence or presence of UV-B. UV-B-untreated microalgae were used as the control. Comparative physiological responses, including photosynthetic pigments and non-enzymatic antioxidants, as well as nicotine and nicotyrine removal, were evaluated in 7-day cultures. UV-B treatments did not negatively impact algal chlorophyll or carotenoid production. UV-B acclimation was strain-dependent, correlating with native environment adaptations and genetic constitutions. UV-B as a pretreatment had long-term positive effects on non-enzymatic antioxidant capacity. However, LG1 needed more time to readjust the pro-oxidant/antioxidant balance, as it was the most UV-B-sensitive. Phenolic compounds played an important role in the antioxidant system response to UV-B, while flavonoids did not contribute to the total antioxidant capacity. Although cross-resistance between UV-B and CBW was observed in F4 and R1, only R1 showed nicotine/nicotyrine catabolism induction due to UV-B. Overall, the results suggest that UV-B activates defense pathways associated with resistance or tolerance to nicotine and nicotyrine.

Remediation Capacity of Different Microalgae in Effluents Derived from the Cigarette Butt Cleaning Process.

Microalgal-based remediation is an ecofriendly and cost-effective system for wastewater treatment. This study evaluated the capacity of microalgae in the remediation of wastewater from cleaning process of smoked cigarette butts (CB). At laboratory scale, six strains (one from the family Scenedesmaceae, two Chlamydomonas debaryana and three Chlorella sorokiniana) were exposed to different CB wastewater dilutions to identify toxicity levels reflected in the alteration of microalgal physiological status and to determine the optimal conditions for an effective removal of contaminants. CB wastewater could impact on microalgal chlorophyll and carotenoid production in a concentration-dependent manner. Moreover, the resistance and remediation capacity did not only depend on the microalgal strain, but also on the chemical characteristics of the organic pollutants. In detail, nicotine was the most resistant pollutant to removal by the microalgae tested and its low removal correlated with the inhibition of photosynthetic pigments affecting microalgal growth. Concerning the optimal conditions for an effective bioremediation, this study demonstrated that the Chlamydomonas strain named F2 showed the best removal capacity to organic pollutants at 5% CB wastewater (corresponding to 25 butts L−1 or 5 g CB L−1) maintaining its growth and photosynthetic pigments at control levels.

Growth and proximate composition of Pleurotus ostreatuscultivated on green bocaiuva pulp substrates with different nitrogen sources

The aim of this work was to evaluate the growth and the proximate compositionof the mycelium-based bocaiuva pulp with the edible mushroom Pleurotusostreatuson green bocaiuva flour added with different sources of nitrogen (urea, ammonium nitrate and sulfate ammonia). Growth was monitored by kinectics. At the end, the proximate composition of the best three treatments (dehydrated green bocaiuva pulp and water, T1; dehydrated green bocaiuva pulp and ammonium nitrate, T3; and green bocaiuva pulp/wheat bran and ammonium nitrate, T7) was determined. Ammonium nitrate was the nitrogen source that showed the greatest growth in both substrates (T3:8.33 cm and T7:7.67 cm) in relation to the other treatments (4.67 to 7.17 cm), with emphasis on the green bocaiuva pulp. The substrate with green bocaiuva pulp and water was the one that showed the highest growth (7.50 cm), which was close to the treatment with mixed substrate and ammonium nitrate (7.67 cm). The treatment with the green bocaiuva pulp and ammonium nitrate (T3) was highlighted due to its significant increase in proteins (9.42 g 100 g-1) and fibers (5.21 g 100 g-1), and decrease in carbohydrates (9.52 g 100 g-1), in comparison to the other treatments T7 (8.94, 2.16, and 5.99 g 100 g-1, respectively) and T1 (2.78, 4.33, and 2.28 g 100 g-1, respectively). The product obtained from the growth of P. ostreatusin green bocaiuva pulp presents promising perspectives to be utilized as raw material for the development of new food products with added nutritional value.

Evaluation of the Fermentative Capacity of Saccharomyces cerevisiae CAT-1 and BB9 Strains and Pichia kudriavzevii BB2 at Simulated Industrial Conditions.

The search for promising yeasts that surpass the fermentative capacity of commercial strains, such as Saccharomyces cerevisiae CAT-1, is of great importance for industrial ethanol processes in the world. Two yeasts, Pichia kudriavzevii BB2 and Saccharomyces cerevisiae BB9, were evaluated in comparison to the industrial yeast S. cerevisiae CAT-1. The objective was to evaluate the performance profile of the three studied strains in terms of growth, substrate consumption, and metabolite formation, aiming to determine their behaviour in different media and pH conditions. The results showed that under cultivation conditions simulating the medium used in the industrial process (must at 22° Brix at pH 3.0) the highest ethanol productivity was 0.41 g L-1 h-1 for S. cerevisiae CAT-1, compared to 0.11 g L-1 h-1 and 0.16 g L-1 h-1 for P. kudriavzevii and S. cerevisiae BB2, respectively. S. cerevisiae CAT-1 produced three times more ethanol in must at pH 3.0 (28.30 g L-1) and in mineral medium at pH 3.0 (29.17 g L-1) and 5.0 (30.70 g L-1) when compared to the value obtained in sugarcane must pH 3.0 (9.89 g L-1). It was concluded that S. cerevisiae CAT-1 was not limited by the variation in pH in the mineral medium due to its nutritional composition, guaranteeing better performance of the yeast even in the presence of stressors. Only S. cerevisiae CAT-1 expressed he constitutive invertase enzyme, which is responsible for hydrolysing the sucrose contained in the must.

Effects of the carbon source on the physiology and invertase activity of the yeast Saccharomyces cerevisiae FT858.

Saccharomyces cerevisiae FT858 is an industrial yeast strain with high fermentative efficiency, but marginally studied so far. The aim of this work was to evaluate the biotechnological potential of S. cerevisiae FT858 through kinetic growth parameters, and the influence of the concentration of the substrate on the synthesis of the invertase enzyme. Invertases have a high biotechnological potential and their production through yeast is strongly influenced by the sugars in the medium. S. cerevisiae FT858 has an excellent biotechnological potential compared to the industrial yeast reference S. cerevisiae CAT-1, as it presented a low glycerol yield on the substrate (Y GLY/S) and a 10% increase in ethanol yield on sucrose in cultures with sucrose at 37 °C. The substrate concentration directly interfered in invertase production and the enzymatic expression underwent strong regulation through glucose concentration in the culture medium and S. cerevisiae CAT-1 presented constitutive behavior for the invertase enzyme.

Influence of luminosity, carbon source and concentration of salts in the physiology of Chlorella sorokiniana.

Growth studies are important to increase the knowledge about the physiology of microalgae. The development of suitable culture media allows optimum growth to each species. The genus Chlorella has the ability to adapt to various environmental and nutritional conditions. Thus, the aim of this work was to evaluate the physiology of Chlorella sorokiniana CTT 7727 at different growth conditions with Basal Bold (BB) medium. For that, heterotrophic, autotrophic and mixotrophic cultures were carried out. The maximum specific growth rates (µmax), the maximum biomass concentrations (Xmax) and cell productivities (PX) were calculated for each experiment. Among all the treatments evaluated, that with 24 h light, 3x BB (g L-1) and CO2 presented a higher µmax (0.40 day-1) and maximum cell concentration due the increased concentration of nutrients. Replacement of dark to light has increased Xmax from 2.3 × 105 to 9.3 × 106 cells mL-1 in regular BB medium and 3.6 × 105 to 2.1 × 107 cells mL-1 in 3x BB medium in autotrophic cultivations. The PX increased from 2.4 × 104 cells mL-1 h-1 (1x BB (g L-1)) to 3.6 × 104 cells mL-1 h-1 (3x BB (g L-1)), in the presence of 24 light and CO2. However, the same behaviour was not observed when BB concentration was increased 6, 8 or 10 times the initial concentration of BB medium. Experiments with pulses of concentrated nutrients showed that declining cells can resume their growth after nutrient depletion, but the viability is decreased after successive pulses.

Effects of the carbon source and the interaction between carbon sources on the physiology of the industrial Saccharomyces cerevisiae CAT-1.

During industrial fermentation, wild isolates are able to persist and even predominate in the bioreactors. Saccharomyces cerevisiae CAT-1 was one of these isolates and now is one of the yeasts mostly used in industrial ethanol processes in Brazil due to its efficient fermentation capacity. Despite it, the strain's physiology has been marginally studied so far. Since strains of the same species may have different responses to a specific cultivation condition, this work aimed to evaluate the physiology of S. cerevisiae CAT-1 in batch cultures using different carbon sources (glucose, fructose, sucrose, maltose, and galactose) as a sole carbon source and in binary mixtures, at 30 and 37 °C. The results showed that the fructose, sucrose, and maltose were the sugars that presented the highest ethanol yields on the substrate (0.40 gethanol gsubstrate-1) at both temperatures. Galactose was the sugar that the yeast had the lowest affinity given the lowest maximum specific growth rate (0.28 h-1). Despite the influence of a variety of mechanisms for sugar transport, the cells consume first substrates with fewer metabolic steps to catabolism and are susceptible to adaptive evolution depending on the availability of substrate.

Development and characterization of biopolymer films based on bocaiuva (Acromonia aculeata) flour.

This work aimed to produce films based on bocaiuva flour (Acrocomia aculeata) by the casting method, and to characterise them. All obtained films were visually symmetrical, without ruptures or blistering and visually homogeneous, easy to handle with a yellowish colouration. The addition of glycerol allowed greater flexibility to the films. The tensile strength and the elongation increase as the concentration of flour increased (2.04 g 100 mL-1). The addition of oily phases increases the elongation, indicating that the essential oil incorporated into the films acted as plasticizer because it also allowed a greater permeability to water vapor. Peaks at 2Ɵ between 10.00°, 13.81°, 17.67°, 20.0° and 24.34° were observed in films with 12.56 g of starch per 100 g of pulp, which are characteristic of B-starch, due to the presence of long branched chains of amylopectin, with a peak characteristic of lignocellulosic materials. Reflection was more intense at 2Ɵ between 22° for all treatments. The obtained films presented relevant characteristics for the application as edible coating.

Control of pathogens in fresh pork sausage by inclusion of Lactobacillus sakei BAS0117.

A pork sausage was produced with low sodium content (1.64%) to which Lactobacillus sakei was added with the aim of developing a meat pork sausage for cooking and having technological, organoleptic, and hygienic advantages. The lactic acid bacteria (LAB) L. sakei, Lactococcus sp., and Pediococcus pentosaceus were submitted to extreme pH, temperature, and NaCl conditions. Lactobacillus sakei was used in pork sausage because of its resistance to different culture conditions and its antimicrobial potential. The food-borne pathogens Listeria monocytogenes Scott A, Enterococcus faecalis, and Staphylococcus aureus were used as indicator microorganisms to evaluate the antimicrobial activity of selected LAB strains. Salmonella enterica serotype Choleraesuis is a common pathogen of pigs. To the raw sausage product containing L. sakei and nonpathogenic endogenous microbiota, we added about >104 and <105 CFU/g of S. enterica serotype Choleraesuis to evaluate the inhibitory potential of L. sakei towards this pathogen. Salmonella Choleraesuis was inhibited in the presence of L. sakei over 7 days of storage of the meat product (about 3.0 log cycles reduction). Lactobacillus sakei significantly increased inhibition when compared with the nonfermented sausage. Thus, L. sakei BAS0117 played an important role as an additional hurdle in the fermented meat pork sausage during storage.

Physiology of yeast strains isolated from Brazilian biomes in a minimal medium using fructose as the sole carbon source reveals potential biotechnological applications.

The aim of this study was to evaluate the kinetic parameters and the production of metabolites of 13 novel yeasts isolated from a distillery and fruits, and Saccharomyces cerevisiae CAT-1, cultivated in fructose-based medium. The yeasts with the highest µ max were obtained from must, Pichia kudriavzevii BB2, P. kudriavzevii BB1, and S. cerevisiae BB9 (0.47-0.49 h-1). S. cerevisiae CAT-1 (3.02 g gDCM-1 h-1), S. cerevisiae BB9 (3.01 g gDCM-1 h-1), and Candida glabrata Recol 41 (2.52 g gDCM-1 h-1) stood out in terms of µ S. C. parapsilosis Recol 29, and Rhodotorula mucilaginosa Recol 03 strains showed the highest Y X/S (0.30 and 0.28 gDCM g-1, respectively). C. glabrata Recol 10 and S. cerevisiae BB9 strains stood out for their higher substrate conversion rates into ethanol (0.44 and 0.41 gEth gS-1, respectively). R. mucilaginosa Recol 03 presented the poorest performance in substrate consumption (0.87 g gDCM-1 h-1), while the strains isolated from must and C. glabrata Recol 10 showed the highest ethanol production and the C. parapsilosis Recol 29 showed the highest biomass conversion.

Catalytic and thermodynamic properties of ß-glucosidases produced by Lichtheimia corymbifera and Byssochlamys spectabilis.

The objective of the present study was to optimize parameters for the cultivation of Lichtheimia corymbifera (mesophilic) and Byssochlamys spectabilis (thermophilic) for the production of ß-glucosidases and to compare the catalytic and thermodynamic properties of the partially purified enzymes. The maximum amount of ß-glucosidase produced by L. corymbifera was 39 U/g dry substrate (or 3.9 U/mL), and that by B. spectabilis was 77 U/g (or 7.7 U/mL). The optimum pH and temperature were 4.5 and 55 °C and 4.0 and 50 °C for the enzyme from L. corymbifera and B. spectabilis, respectively. ß-Glucosidase produced by L. corymbifera was stable at pH 4.0-7.5, whereas the enzyme from B. spectabilis was stable at pH 4.0-6.0. Regarding the thermostability, ß-glucosidase produced by B. spectabilis remained stable for 1 h at 50 °C, and that from L. corymbifera was active for 1 h at 45 °C. Determination of thermodynamic parameters confirmed the greater thermostability of the enzyme produced by the thermophilic fungus B. spectabilis, which showed higher values of ΔH, activation energy for denaturation (Ea), and half-life t(1/2). The enzymes were stable in the presence of ethanol and were competitively inhibited by glucose. These characteristics contribute to their use in the simultaneous saccharification and fermentation of vegetable biomass.

Biochemical characterization and evaluation of invertases produced from Saccharomyces cerevisiae CAT-1 and Rhodotorula mucilaginosa for the production of fructooligosaccharides.

Invertases are used for several purposes; one among these is the production of fructooligosaccharides. The aim of this study was to biochemically characterize invertase from industrial Saccharomyces cerevisiae CAT-1 and Rhodotorula mucilaginosa isolated from Cerrado soil. The optimum pH and temperature were 4.0 and 70 °C for Rhodotorula mucilaginosa invertase and 4.5 and 50 °C for Saccharomyces cerevisiae invertase. The pH and thermal stability from 3.0 to 10.5 and 75 °C for R. mucilaginosa invertase, respectively. The pH and thermal stability for S. cerevisiae CAT-1 invertase from 3.0 to 7.0, and 50 °C, respectively. Both enzymes showed good catalytic activity with 10% of ethanol in reaction mixture. The hydrolysis by invertases occurs predominantly when sucrose concentrations are ≤5%. On the other hand, the increase in the concentration of sucrose to levels above 10% results in the highest transferase activity, reaching about 13.3 g/L of nystose by S. cerevisiae invertase and 12.6 g/L by R. mucilaginosa invertase. The results demonstrate the high structural stability of the enzyme produced by R. mucilaginosa, which is an extremely interesting feature that would enable the application of this enzyme in industrial processes.

Screening of an adapted culture medium composed by different carbon sources for heterotrophic cultivation of Chlorella vulgaris using a microplate assay / Triagem de um meio de cultura adaptado composto por diferentes fontes de carbono para o cultivo heterotrófico de Chlorella vulgaris usando um ensaio de microplacas

The ability of microalgae to grow heterotrophically lies in the ability to oxidize organic compounds present in the external environment. The aim of this work was to evaluate the growth of Chlorella vulgaris under heterotrophic culture conditions using Basal Bold and NPK media supplemented with different sole carbon sources (glucose, fructose, sucrose, glycerol or acetate). The kinetic parameters obtained were maximum specific growth rate (μmax), doubling time (DT), maximal absorbance, which was also converted to cell concentration values using a linear relation, and cell productivity (PX). Among all the treatments analyzed, the highest maximum specific growth rate found was 0.030 hour-1 (0.72 day-1) in the treatment using Basal Bold medium supplemented with glucose. The highest cellular concentration and cell productivity were also found for this same treatment (4.03 x 106 cell mL-1 and 64.0 x 106 cell L-1 day-1, respectively). It was concluded that that the Basal Bold medium was more efficient for Chlorella vulgaris growth, since it induced higher values of μmax and cellular concentration. Results obtained were very reproducible using microplate assay.

A capacidade das microalgas de crescer heterotroficamente reside na habilidade de oxidar compostos orgânicos presentes no ambiente externo. O objetivo deste trabalho foi avaliar o crescimento de Chlorella vulgaris em condições heterotróficas de cultura, usando meios Basal Bold e NPK, suplementados com diferentes fontes de carbono (glicose, frutose, sacarose, glicerol ou acetato). Os parâmetros cinéticos obtidos foram a velocidade específica máxima de crescimento (μmax), tempo de duplicação (TD), absorbância máxima, sendo que esta última também foi convertida em valores de concentração celular, usando uma relação linear e produtividade celular (PX). Entre todos os tratamentos analisados, a maior velocidade específica máxima de crescimento encontrada foi de 0,030 h-1 (0,72 dia-1) no tratamento usando o meio Basal Bold suplementado com glicose. A maior concentração celular e a maior produtividade celular também foram encontradas para esse mesmo tratamento (4,03 x 106 cel mL-1 e 64,0 x 106 cel L-1 dia-1, respectivamente). Concluiu-se que o meio Basal Bold foi mais eficiente para o crescimento de Chlorella vulgaris, pois induziu valores mais elevados de μmax e de concentração celular. Os resultados obtidos foram muito reproduzíveis, utilizando o ensaio de microplacas.

Influence of Adding Recovered Protein from Processing Wastewater on the Quality of Mechanically Separated Chicken Meat Surimi Like-Material.

Functional and nutritional soluble proteins can be recovered from surimi (and surimi-like material) processing wastewater, reducing environmental problems and the cost of an irresponsible waste disposal. Recovered proteins may be added back at a low percentage to surimi products. The aim of this work was to evaluate the effect of the addition of soluble recovered proteins (RP), obtained from mechanically separated chicken meat surimi-like material (MSCM-SLM) processing wastewater by acidic pH-shifting, on the composition and texture of RP-MSCM-SLM, with RP contents of 0, 10, 20 and 30% (w/w) in the mixture. For that, proximate composition and gel properties were evaluated. The fat content of the MSCM-SLM was significantly reduced to 11.98% and protein increased to 83.64% (dry basis) after three washing cycles. The addition of 30% RP in the MSCM-SLM significantly augmented the protein content to 93.45% and reduced fat content from to 2.78%. On the other hand, the addition of RP was responsible for a drastic decrease in texture parameters, reaching 252.36 g, 185.23 g.cm, and 6.97 N for breaking force, gel strength and cutting strength, respectively, when 30% of RP was included in the MSCM-SLM. It was concluded that the obtained intermediary product (RP-MSCM-SLM) is a good option to applications in processed meat products where high texture parameters are dispensable, e.g., emulsified inlaid frankfurter-type sausages, but high protein content and low fat content desired.

Catalytic Properties of Amylolytic Enzymes Produced by Gongronella butleri Using Agroindustrial Residues on Solid-State Fermentation.

Amylases catalyze the hydrolysis of starch, a vegetable polysaccharide abundant in nature. These enzymes can be utilized in the production of syrups, alcohol, detergent, pharmaceutical products, and animal feed formulations. The aim of this study was to optimize the production of amylases by the filamentous fungus Gongronella butleri by solid-state fermentation and to evaluate the catalytic properties of the obtained enzymatic extract. The highest amylase production, 63.25 U g-1 (or 6.32 U mL-1), was obtained by culturing the fungus in wheat bran with 55% of initial moisture, cultivated for 96 h at 25°C. The enzyme presented optimum activity at pH 5.0 and 55°C. The amylase produced was stable in a wide pH range (3.5-9.5) and maintained its catalytic activity for 1 h at 40°C. Furthermore, the enzymatic extract hydrolyzed starches from different vegetable sources, presenting predominant dextrinizing activity for all substrates evaluated. However, the presence of glucose was observed in a higher concentration during hydrolysis of corn starch, indicating the synergistic action of endo- and exoamylases, which enables the application of this enzymatic extract to produce syrups from different starch sources.

Production, characterization, and evaluation of the stability of biodiesel obtained from greasy agroindustrial waste during storage.

Greasy agroindustrial waste from the process of cooking hog meat was used to produce biodiesel (fatty acid methyl esters and fatty acid ethyl esters) under a specific storage condition. The operating conditions necessary to achieve the optimal relationship between quality and productivity were assessed. Next, batches of methyl and ethyl biodiesels were produced, generating 2 L of each product to evaluate their stability during 150 days of storage. The following study indicates that, for methyl route, the molar ratio (1:5) and catalyst (0.5%) yielded the best result of 90.77% (w/v) and quality parameters within the international standards. The ethyl route also showed the highest yield (77.09% w/v) and better quality parameters with a molar ratio (1:5) and catalyst (0.5%). No significant differences were observed in the methyl biodiesel obtained from the batch process for up to 45 days, while the ethyl biodiesel degraded in 30 days of storage.

Production and Catalytic Properties of Amylases from Lichtheimia ramosa and Thermoascus aurantiacus by Solid-State Fermentation.

The present study compared the production and the catalytic properties of amylolytic enzymes obtained from the fungi Lichtheimia ramosa (mesophilic) and Thermoascus aurantiacus (thermophilic). The highest amylase production in both fungi was observed in wheat bran supplemented with nutrient solution (pH 4.0) after 96 hours of cultivation, reaching 417.2 U/g of dry substrate (or 41.72 U/mL) and 144.5 U/g of dry substrate (or 14.45 U/mL) for L. ramosa and T. aurantiacus, respectively. The enzymes showed higher catalytic activity at pH 6.0 at 60°C. The amylases produced by L. ramosa and T. aurantiacus were stable between pH 3.5-10.5 and pH 4.5-9.5, respectively. The amylase of L. ramosa was stable at 55°C after 1 hour of incubation, whereas that of T. aurantiacus maintained 60% of its original activity under the same conditions. Both enzymes were active in the presence of ethanol. The enzymes hydrolyzed starch from different sources, with the best results obtained with corn starch. The enzymatic complex produced by L. ramosa showed dextrinizing and saccharifying potential. The enzymatic extract produced by the fungus T. aurantiacus presented only saccharifying potential, releasing glucose monomers as the main hydrolysis product.

Production of xylanase by a new strain of Thermoascus aurantiacus: obtainment of enzymatic extract with reduced cellulolytic activity for application in pulp and paper industries / Produção de xilanase por nova linhagem de Thermoascus aurantiacus: obtenção de extrato enzimático com reduzida atividade celulolítica para aplicação em indústria de papel e celulose

Xylanases are useful in several industrial segments, including pulp and paper bleaching, animal feed, and bread-making processes. However, the industrial use of these enzymes is closely related to its production cost and its catalytic properties. The process of solid state fermentation enables the use of agro-industrial residues as substrates for microbial cultivation and enzymes production, reducing costs. In the present study, different cultivation parameters were evaluated for the xylanase production by the thermophilic fungus Thermoascus aurantiacus, by solid state fermentation, using agro-industrial residues as substrates. High production of xylanase (1701.9 U g-1 of dry substrate) was obtained using wheat bran containing 65% of initial moisture, at 120 h of cultivation, and 45°C. The xylanase showed optimal activity at pH 5.0 and 75°C; its stability was maintained at pH 3.0­11.0. The enzyme retained its catalytic potential after 1 h, at 75°C. The enzymatic extract produced under optimized conditions showed reduced activities of endoglucanase and FPase. Our results, including the xylanase production by T. aurantiacus in low-cost cultivation medium, high structural stability of the enzyme, and reduced cellulolytic activity, encourage the application of this enzymatic extract in pulp and paper bleaching processes.

As xilanases apresentam aplicabilidade em diferentes segmentos industriais, como: branqueamento de papel e celulose, ração animal e panificação. No entanto, a utilização industrial dessas enzimas está intimamente relacionada com seu custo de produção e suas propriedades catalíticas. O processo de fermentação em estado sólido possibilita o uso de resíduos agroindustriais como substratos, para o cultivo microbiano e produção de enzimas, reduzindo o custo da produção enzimática. No presente trabalho, diferentes parâmetros de cultivo foram avaliados para produção de xilanase por cultivo em estado sólido do fungo termófilo Thermoascus aurantiacus, utilizando resíduos agroindustriais como substratos. A maior produção de xilanase, 1701,9 U g-1 de substrato seco, foi obtida no cultivo em farelo de trigo, contendo 65% de umidade inicial, em 120 horas de cultivo a 45°C. A xilanase produzida apresentou atividade ótima em pH 5,0 a 75°C, mantendo sua estabilidade em pH 3,0 a 11,0. A enzima manteve seu potencial catalítico após 1 h a 75°C. O extrato enzimático produzido nas condições otimizadas apresentou reduzida atividade de endoglucanase e FPase. Os resultados obtidos no presente trabalho (produção de xilanase pelo fungo em meios de cultivo de baixo custo, elevada estabilidade estrutural da enzima e reduzida atividade celulolítica) estimulam a aplicação desse complexo enzimático em processos de branqueamento de papel e celulose.