The use of mesophilic and lactic acid bacteria strains as starter cultures for improvement of coffee beans wet fermentation.

The use of starter cultures during food fermentation aims to standardize the process and to obtain a higher quality product. The objectives were to study mesophilic bacteria (MB) and lactic acid bacteria (LAB) isolated from wet coffee processing and evaluate their performance in a pulped coffee medium. Eighty-six bacteria isolates (59 MB and 27 LAB) were assessed for pectinolytic activity, metabolite production, and pH value decrease in coffee-based culture (CPM). Seven bacteria strains (3 MB and 4 LAB) were selected and used as starter cultures in the wet fermentation of pulped coffee. The MB and LAB populations varied from 4.48 to 8.43 log CFU g-1 for MB and 3.54 to 8.72 log CFU g-1 for LAB during fermentation. Organic acid concentration (ranged from 0.01 to 0.53 for succinic acid; 0.71 to 8.14 for lactic acid and 0.06 to 0.29 for acetic acid), and volatile compounds (44 compounds were detected in green beans and 98 in roasted beans) were evaluated during fermentation. The most abundant compounds found in roasted beans belong to furans [15], ketones and esters [14], pyridines [13], and pyrazines [12]). Leuconostoc mesenteroides CCMA 1105 and Lactobacillus plantarum CCMA 1065 presented volatile compounds important for coffee aroma. Isovaleric acid; 2,3-butanediol; phenethyl alcohol; ß-linalool; ethyl linoleate; and ethyl 2-hydroxypropanoate could improve cupping qualities.

Sugarcane bagasse hydrolysis using yeast cellulolytic enzymes.

Ethanol fuel production from lignocellulosic biomass is emerging as one of the most important technologies for sustainable development. To use this biomass, it is necessary to circumvent the physical and chemical barriers presented by the cohesive combination of the main biomass components, which hinders the hydrolysis of cellulose and hemicellulose into fermentable sugars. This study evaluated the hydrolytic capacity of enzymes produced by yeasts, isolated from the soils of the Brazilian Cerrado biome (savannah) and the Amazon region, on sugarcane bagasse pre-treated with H2SO4. Among the 103 and 214 yeast isolates from the Minas Gerais Cerrado and the Amazon regions, 18 (17.47%) and 11 (5.14%) isolates, respectively, were cellulase-producing. Cryptococcus laurentii was prevalent and produced significant ß- glucosidase levels, which were higher than the endo- and exoglucanase activities. In natura sugarcane bagasse was pre-treated with 2% H2SO4 for 30 min at 150oC. Subsequently, the obtained fibrous residue was subjected to hydrolysis using the Cryptococcus laurentii yeast enzyme extract for 72 h. This enzyme extract promoted the conversion of approximately 32% of the cellulose, of which 2.4% was glucose, after the enzymatic hydrolysis reaction, suggesting that C. laurentii is a good ß-glucosidase producer. The results presented in this study highlight the importance of isolating microbial strains that produce enzymes of biotechnological interest, given their extensive application in biofuel production.