Microparticle-enhanced lignocellulolytic enzyme production using DDGS as the main fermentation feedstock

Distillers dried grains with solubles (DDGS) is a byproduct of corn ethanol production which has shown to be an efficient microbial medium for cellulase and xylanase production. These hydrolytic enzymes are crucial in production of lignocellulosic biofuels. Therefore, different strategies to increase the production and quality of such enzymes should be explored. In this study, the effect of microparticles on the enzyme production levels was analyzed using acid hydrolyzed DDGS as the base media. The microparticles, i.e. aluminum oxide and magnesium silicate (talc) were assessed on different days of fungal fermentation at 250 ml shake flask level and 2 L bioreactor level. It was determined that the addition of 5 g/L of aluminum oxide can increase cellulase production from 0.52±0.02 to 1.15±0.04 IU/ml on day 9 in a shake flask. The addition of 10 g/L of aluminum oxide increased the cellulase production from 0.77±0.05 to 0.93±0.01 IU/ml on day 9 in the bioreactor. The xylanase production levels also increased on day 3 from 11.65±0.1 to 21.73±1.98 IU/ml with aluminum oxide particles. The microscopic study of the fungal broth showed a positive change in the mycelial morphology such as a decrease in the dense branching of A. niger mycelia with increasing concentration of microparticles. In addition, it was also concluded that aluminum oxide is a better microparticle than talc in terms of enzyme production levels (121% higher in case of cellulase and 86% for xylanase). Future studies should focus on the optimization of microparticles concentration for enzyme production along with scale-up studies.