Effect of Soaking in Aqueous Ammonia (SAA) Pretreatment on Switchgrass for Production of Cellulases Using Trichoderma reesei Rut C-30

Abstract

<abstract> <bold><sc>Abstract.</sc></bold> Pretreatment plays an important role in the disintegration of phenolic compounds (in the form of lignin) from lignocellulosic feedstock. The effect of 4.5 wt% soaking in aqueous ammonia (SAA) on switchgrass was evaluated for cellulase production using Trichoderma reesei Rut C-30 at 27°C for 168 h. The cellulase production of SAA-treated switchgrass was compared with Solka-Floc and untreated switchgrass. Enzyme activities of 2.99, 1.34, and 0.37 FPU mL^-1 were observed for Solka-Floc, SAA-treated switchgrass, and untreated switchgrass, respectively, at 168 h of fermentation. Controlled environmental conditions had a significant effect on cellulase production using T. reesei. In a 7 L bioreactor (4 L working volume) using SAA-treated switchgrass and T. reesei with a controlled pH of 5 and aeration rate of 1 vvm (volumetric volume per minute), cellulase activity of 1.80 FPU mL^-1 was calculated at 168 h. The produced enzyme broth was evaluated for enzymatic saccharification of SAA-treated switchgrass. The enzymatic saccharification efficiency of T. reesei broth (with and without externally added β-glucosidase) was compared with the commercial enzyme Accellerase 1500 at 50°C for 72 h. Total polysaccharide conversions of 33, 49, and 43 wt% were observed with Accellerase 1500 (80 FPU g^-1 biomass), T. reesei Rut C-30 broth (4.75 FPU g^-1 biomass), and T. reesei Rut C-30 broth with externally added β-glucosidase (4.75 FPU g^-1 biomass + 45 pNPG g^-1 biomass), respectively, over 72 h of enzyme hydrolysis.