Comprehensive Optimization of Culture Conditions for Production of Biomass-Hydrolyzing Enzymes of Trichoderma SG2 in Submerged and Solid-State Fermentation.

Lignocellulose biomass contain large macromolecules especially cellulose and hemicelluloses that can be converted to fuel and chemicals using microbial biocatalysts. This study presents comprehensive optimization of production of biomass-hydrolyzing enzymes (BHE) by a high ß-glucosidase-producing Trichoderma SG2 for bioconversion of lignocellulose biomass. Overall, a mixture of paper powder and switchgrass was most suited for production of BHE in submerged fermentation (SmF). BHE production was significantly different for various organic and inorganic nitrogen sources. The combination of peptone, yeast extract, and ammonium sulfate resulted in the highest activities (Units/mL) of BHE: 9.85 ± 0.55 cellulase, 38.91 ± 0.31 xylanase, 21.19 ± 1.35 ß-glucosidase, and 7.63 ± 0.31 ß-xylosidase. Surfactants comparably enhanced BHE production. The highest cellulase activity (4.86 ± 0.55) was at 25 °C, whereas 35 °C supported the highest activities of xylanase, ß-glucosidase, and ß-xylosidase. A broad initial culture pH (4-7) supported BHE production. The Topt for cellulase and xylanase was 50 °C. ß-xylosidase and ß-glucosidase were optimally active at 40 and 70 °C, respectively; pH 5 resulted in highest cellulase, ß-glucosidase, and ß-xylosidase activities; and pH 6 resulted in highest xylanase activity. Response surface methodology (RSM) was used to optimize major medium ingredients. BHE activities were several orders of magnitude higher in solid-state fermentation (SSF) than in SmF. Therefore, SSF can be deployed for one-step production of complete mixture of Trichoderma SG2 BHE for bioconversion of biomass to saccharide feedstock.

Value-added probiotic development by high-solid fermentation of sweet potato with Saccharomyces boulardii.

Controlled fermentation of Sweet potato (Ipomoea batatas) var. Beauregard by yeast, Saccharomyces boulardii (MAY 796) to enhance the nutritional value of sweet potato was investigated. An average 8.00 × 1010 Colony Forming Units (CFU)/g of viable cells were obtained over 5-day high-solid fermentation. Yeast cell viability did not change significantly over time at 4°C whereas the number of viable yeast cells reduced significantly at room temperature (25°C), which was approximately 40% in 12 months. Overall, the controlled fermentation of sweet potato by MAY 796 enhanced protein, crude fiber, neutral detergent fiber, acid detergent fiber, amino acid, and fatty acid levels. Development of value-added sweet potato has a great potential in animal feed and human nutrition. S. boulardii- fermented sweet potato has great potential as probiotic-enriched animal feed and/or functional food for human nutrition.

Selection and molecular characterization of cellulolytic-xylanolytic fungi from surface soil-biomass mixtures from Black Belt sites.

Plant biomass is an abundant renewable natural resource that can be transformed into chemical feedstocks. Enzymes used in saccharification of lignocellulosic biomass are a major part of biofuel production costs. A cocktail of cellulolytic and xylanolytic enzymes are required for optimal saccharification of biomass. Accordingly, thirty-two fungal pure cultures were obtained from surface soil-biomass mixtures collected from Black Belt sites in Alabama by culturing on lignocellulosic biomass medium. The fungal strains were screened for the coproduction of cellulolytic and xylanolytic enzymes. Strains that displayed promising levels of cellulolytic and xylanolytic enzymes were characterized by molecular analysis of DNA sequences from the large subunit and internal transcribed spacer (ITS) of their ribosomal RNA gene. Nucleotide sequence analysis revealed that two most promising isolates FS22A and FS5A were most similar to Penicillium janthinellum and Trichoderma virens. Production dynamics of cellulolytic and xylanolytic enzymes from these two strains were explored in submerged fermentation. Volumetric productivity after 120 h incubation was 121.08 units/L/h and 348 units/L/h for the filter paper cellulase and xylanase of strain FS22A, and 90.83 units/L/h and 359 units/L/h, respectively for strain FS5A. Assays with 10 times dilution of enzymes revealed that the activities were much higher than that observed in the crude culture supernatant. Additionally, both FS22A and FS5A also produced amylase in lignocellulose medium. The enzyme profiles of these strains and their activities suggest potential applications in cost effective biomass conversion and biodegradation.

Enhanced ethanol production from Kinnow mandarin (Citrus reticulata) waste via a statistically optimized simultaneous saccharification and fermentation process.

Dried, ground, and hydrothermally pretreated Kinnow mandarin (Citrus reticulata) waste was used to produce ethanol via simultaneous saccharification and fermentation (SSF). Central composite design was used to optimize cellulase and pectinase concentrations, temperature, and time for SSF. The D-limonene concentration determined with high-performance liquid chromatography (HPLC) for fresh, dried, and pretreated biomass was 0.76%, 0.32%, and 0.09% (v/w), respectively. Design Expert software suggested that the first-order effect of all four factors and the second-order effect of cellulase and pectinase concentrations were significant for ethanol production. The validation experiment using 6 FPU gds(-1) cellulase and 60 IU gds(-1) pectinase at 37 °C for 12 h in a laboratory batch fermenter resulted in ethanol concentration and productivity of 42 g L(-1) and 3.50 g L(-1) h(-1), respectively. Experiments using optimized parameters resulted in an ethanol concentration similar to that predicted by the model equation and also helped reduce fermentation time.