Hidrólise enzimática de sorgo sacarino por enzimas produzidas em mono e cocultivo entre fungos e actinobactérias

Abstract

The present study evaluated the effectiveness of enzymes produced by microorganisms in mono and co-cultures between fungi and actinobacteria to hydrolyze the biomass of sweet sorghum cultivar CMSXS5021 chemically pre-treated with diluted acid and base aiming at the production of second-generation ethanol. In addition, the sorghum biomass was characterized to obtain the yield in the conversion of sugars. Fifty-four actinobacteria were tested for xylanase production in solid media. Seventeen produced xylanase and were tested for their ability to produce xylanase, FPase, and endoglycanase in submerged culture. The best xylanase-producing strain was S. copoamus, producing 24 IU. ml -1. Streptomyces sp. had the highest FPase production, with 1.12 IU. mL-1 and S. ossamyceticus was the best endoglycanase producer, with 0.99 IU. mL-1. When using sweet sorghum as substrate, S. curacoi, S. ossamyceticus, and S. copoamus showed xylanase activities of 4.5 IU. mL-1, 4.4 IU. mL- and 0.8 IU. mL-1, respectively. No FPase activity was detected under assay conditions for any actinobacteria. Six actinobacteria were selected in co-cultivation, namely: Streptomyces sp., S. curacoi, S. ossamyceticus, S. capoamus, S. chiangmaiensis, and S. thiolutheus. The fungi used were: Aspergillus terreus, Aspergillus acculeatus, Trichoderma reesei, Panus lecomtei, Fistulina hepatica and Flavodon flavus. The microorganisms were cultivated in a mono and co-culture system in Petri dishes containing potato dextrose agar (PDA) medium. S. curacoi showed the best synergism with fungi. The crude extract of the co-culture between S. curacoi and T. reesei showed an FPase activity of 0.48 IU. mL-1. The highest endoglycanase production occurred in the co-culture between S. curacoi and T. reesei, with 0.95 IU. mL-1. For β-glucosidase, the highest production occurred in the co-culture between S. curacoi and A. acculeatus, with 0.85 IU. mL-1. The highest endo-xylanase activity was observed in T. reesei monoculture, with 2.06 IU. mL-1. Finally, the activities of laccase, total peroxidases, and proteases were less than 1 IU. mL-1. When comparing the extracts in co-culture with the commercial cocktails Accellerase® 1500, Cellic CTec3®, Celumax C, and Cellumax®, no statistical difference was observed for Accellerase® 1500, with 22 g. L-1, representing a 48% yield of glucose. Cellic CTec3® followed it with 19 g. L-1 and 40% yield, and the crude extract of the co-cultivation between S. curacoi and T. reesei with 18 g. L-1 and 39% glucose yield. We conclude that (1) actinobacteria have the potential to produce xylanases for use in the agricultural industry; (2) co-culture between fungi and actinobacteria has shown to be promising for processes that require hydrolytic enzymes; and (3) sweet sorghum biomass can be used as a substrate for obtaining enzymes and sugars for fermentation when saccharified by crude enzymatic extracts and commercial cocktails.