Production of flavor-active compounds and physiological impacts in immobilized Saccharomyces spp. cells during beer fermentation.

Yeast immobilization in beer fermentation has recently regained attention, due to the expansion of the craft beer market and the diversification of styles and flavors. The aim of this study was to evaluate the physiological differences between immobilized and free yeast cells with a focus on flavor-active compounds formation. Three strains of Saccharomyces spp. (SY025, SY067, SY001) were evaluated in both free and immobilized (using a cellulose-based support, referred as ImoYeast) forms during static batch fermentations of 12 °P malt extract. Immobilized cells showed higher glycerol (SY025, 40%; SY067, 53%; SY001, 19%) and biomass (SY025, 67%; SY067, 78%; SY001, 56%) yields than free cells. Conversely, free cells presented higher ethanol yield (SY025, 9%; SY067, 9%; SY001, 13%). Flavor-active compounds production exhibited significant alterations between immobilized and free cells systems, for all strains tested. Finally, a central composite design with varying initial biomass (X0) and substrate (S0) concentrations was conducted using strain SY025, which can be helpful to modulate the formation of one or more flavor-active compounds. In conclusion, yeast immobilization in the evaluated support resulted in flavor alterations that can be exploited to produce different beer styles.

Biosurfactant production of Piper hispidum endophytic fungi.

AIMS: To evaluate the production of biosurfactants by fungi isolated from the Amazonian species Piper hispidum (Piperaceae), and to determine the physico-chemical properties of the crude biosurfactant obtained from the most promising fungi. METHODS AND RESULTS: A total of 117 endophytic fungi were isolated, and 50 were used to verify the production of biosurfactants. Of these, eight presented positive results in the drop collapse test, and emulsification index ranging from 20 to 78%. The most promising fungi, Ph III 23L and Ph II 22S (identified as Aspergillus niger and Glomerella cingulata, respectively) were recultivated for extraction and analysis of the biosurfactant's physico-chemical characteristics. The cultivation broth that presented the greatest decrease in surface tension (36%) was that of the A. niger, which reduced it from 68·0 to 44·0 mN m-1 . The lowest critical micellar concentration value was found for the same endophyte (14·93 mg ml-1 ). CONCLUSIONS: Endophytes of P. hispidum proved to be interesting producers of biosurfactants and presented promising physico-chemical characteristics for applications in diverse industrial sectors. SIGNIFICANCE AND IMPACT OF THE STUDY: Piper hispidum endophytic fungi can be used as a new source of biosurfactants, as these molecules present a significant market due to their wide industrial applications.

Artisanal cachaça and brewer's spent grain as sources of yeasts with promising biotechnological properties.

AIMS: This study aimed to characterize yeasts isolated from the environment of artisanal cachaça production and brewer's spent grain-bearing in mind their further application in bioprocesses. METHODS AND RESULTS: Cell morphology, growth and fermentative parameters, and karyotyping were employed for the selection and grouping of yeast strains. The results showed that from 134 yeast strains studied, 14·2% exhibited cells with snowflake morphology, which is not appropriate for bioethanol production. The fermentation in sugarcane syrup was carried out with 71 Saccharomyces cerevisiae, 19 Torulaspora delbrueckii, eight Wickerhamomyces anomalus, six Candida parapsilosis, five Pichia mashurica, three Candida intermedia, two Clavispora lusitaniae and one Candida aaseri. Among the most important ethanol-producing strains, T. delbrueckii LMQA BSG 7 and S. cerevisiae LMQA SNR 65 presented biomass yield, ethanol yield and productivity similar or higher than PE-2 and CAT-1 (bioethanol industrial strains). CONCLUSIONS: This study showed a high potential for industrial application of the strains LMQA SNR 65 (S. cerevisiae) and LMQA BSG 7 (T. delbrueckii). It was found that the use of the chromosomal profile is not adequate to qualify yeasts concerning their technological performance. SIGNIFICANCE AND IMPACT OF THE STUDY: This study reported yeasts isolated from uncommon sources that present significant characteristics for potential application in bioprocesses.

Novel consortium of Klebsiella variicola and Lactobacillus species enhances the functional potential of fermented dairy products by increasing the availability of branched-chain amino acids and the amount of distinctive volatiles.

AIMS: Identify novel bacterial taxa that could increase the availability of branched-chain amino acids and the amount of distinctive volatiles during skim milk fermentation. METHODS AND RESULTS: We recovered 344 bacterial isolates from stool samples of healthy and breastfed infants. Five were selected based on their ability to produce branched-chain amino acids. Three strains were identified as Escherichia coli, one as Klebsiella pneumoniae and other as Klebsiella variicola by molecular and biochemical methods. HPLC and solid-phase microextraction with GC-MS were used for the determination of free amino acids and volatile compounds respectively. The consortium formed by K. variicola and four Lactobacillus species showed the highest production of Leu and Ile in skim milk fermentation. In addition, the production of volatile compounds, such as acetoin, ethanol, 2-nonanone, and acetic, hexanoic and octanoic acids, increased in comparison to commercial yogurt, Emmental and Gouda cheese. Also, distinctive volatiles, such as 2,3-butanediol, 4-methyl-2- hexanone and octanol, were identified. CONCLUSION: The use of K. variicola in combination with probiotic Lactobacillus species enhances the availability of Leu and Ile and the amount of distinctive volatiles during skim milk fermentation. SIGNIFICANCE AND IMPACT OF THE STUDY: The identified consortium increases the functional potential of fermented dairy products.

Microbial dynamics in anaerobic digestion reactors for treating organic urban residues during the start-up process.

Anaerobic digestion of organic residues offers economic benefits via biogas production, still methane (CH4 ) yield relies on the development of a robust microbial consortia for adequate substrate degradation, among other factors. In this study, we monitor biogas production and changes in the microbial community composition in two semi-continuous stirred tank reactors during the setting process under mesophilic conditions (35°C) using a 16S rDNA high-throughput sequencing method. Reactors were initially inoculated with anaerobic granular sludge from a brewery wastewater treatment plant, and gradually fed organic urban residues (4·0 kg VS m-3  day-1 ) . The inocula and biomass samples showed changes related to adaptations of the community to urban organic wastes including a higher relative proportion of Clostridiales, with Ruminococcus spp. and Syntrophomonas spp. as recurrent species. Candidatus Cloacamonas spp. (Spirochaetes) also increased from ~2·2% in the inoculum to >10% in the reactor biomass. The new community consolidated the cellulose degradation and the propionate and amino acids fermentation processes. Acetoclastic methanogens were more abundant in the reactor, where Methanosaeta spp. was found as a key player. This study demonstrates a successful use of brewery treatment plant granular sludge to obtain a robust consortium for methane production from urban organic solid waste in Mexico. SIGNIFICANCE AND IMPACT OF THE STUDY: This study describes the selection of relevant bacteria and archaea in anaerobic digesters inoculated with anaerobic granular sludge from a brewery wastewater treatment plant. Generally, these sludge granules are used to inoculate reactors digesting organic urban wastes. Though, it is still not clearly understood how micro-organisms respond to substrate variations during the reactor start-up process. After feeding two reactors with organic urban residues, it was found that a broader potential for cellulose degradation was developed including Bacteroidetes, Firmicutes and Spirochaetes. These results clarify the bacterial processes behind new reactors establishment for treating organic wastes in urban areas.

Quality improvement and geographical indication of cachaça (Brazilian spirit) by using locally selected yeast strains.

AIMS: In order to improve the quality and to create a biological basis for obtainment of the protected denomination of origin (PDO), indigenous yeast were isolated and characterized for use in Salinas city (the Brazilian region of quality cachaça production). MATERIAL AND METHODS: Seven thousand and two hundred yeast colonies from 15 Salinas city distilleries were screened based on their fermentative behaviour and the physicochemical composition of cachaça. Molecular polymorphic analyses were performed to characterize these isolates. RESULTS: Two Saccharomyces cerevisiae strains (nos. 678 and 680) showed appropriate characteristics to use in the cachaça production: low levels of acetaldehyde and methanol, and high ethyl lactate/ethyl acetate ratio respectively. They also presented polymorphic characteristics more closely related between themselves even when compared to other strains from Salinas. CONCLUSIONS: The application of selected yeast to cachaça production can contribute for the improvement of the quality product as well as be used as a natural marker for PDO. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggests that the use of selected yeast strains could contribute to obtain a cachaça similar to those produced traditionally, while getting wide acceptation in the market, yet presenting more homogeneous organoleptic characteristics, and thus contributing to the PDO implementation.

A new alternative use for coffee pulp from semi-dry process to ß-glucosidase production by Bacillus subtilis.

UNLABELLED: Coffee is among the most preferred nonalcoholic drinks, and its consumption is distributed globally. During the coffee fruiting process, however, a large amount of waste is generated in the form of pulp, mucilage, husks, and water waste. The pulp and mucilage have the chemical composition to support the growth of micro-organisms and the production of value-added product. The aim was testify pulp coffee can be considered as carbon and inductor source for ß-glucosidase by Bacillus subtilis CCMA 0087. The response surface methodology (RSM) based on a central composite rotatable design (CCRD) was employed for this optimization. The methodology used in the optimization process was validated by testing the best conditions obtained and comparing them with the values predicted by the model. The highest ß-glucosidase production (22·59 UI ml(-1) ) was reached in 24 h of culturing at coffee pulp concentration of 36·8 g l(-1) , temperature of 36·6°C, and pH of 3·64. SIGNIFICANCE AND IMPACT OF THE STUDY: Countries whose economy is based on agricultural activities generate a great deal of liquid and solid waste. Thus, it is important to develop new alternatives for using this waste rather than disposing it in the environment. The production of enzymes, and particularly cellulase, is one such alternative. In this study, we proposed to produce ß-glucosidase production from pulp coffee extract using a Bacillus subtilis strain.