Optimization of Lignocellulosic Enzyme production by Microbial Strains: Study of Kinetics and Environmental Influences

Abstract

In the context of valorizing lignocellulosic biomass for biofuel production a mixture of forest residues (FW) and aromatic-medicinal plant wastes (AMPW) was considered in this study to assess its ability to support the production of cellulolytic enzymes by Aspergillus niger, Trichoderma longibrachiatum and Zymomonas mobilis. The residue mixture promoted growth and cellulase production by the microbial strains after 6 days of incubation. Enzymatic activity was determined using filter paper activity (FPase) and endoglucanase carboxymethylcellulase (CMase) assays. Optimization of enzymatic activity was investigated at pH levels (2, 4, 6, 8), various temperatures (22°C, 30°C, 37°C, 45°C) and different inoculum rates (1.5 × 107, 2 × 107 and 2.5 × 107 spores per gram of substrate). Maximum enzymatic activity was observed in Aspergillus niger with FPase and CMCase yields of 23.12 ± 0.1 and 29.78 ± 0.15 U/gds respectively. The highest enzymatic activity was recorded at temperatures of 30°C and 37°C, pH levels of 4 and 6 and with an inoculum rate of 2.5 × 107. The selection of the strain and the optimization of operational conditions are crucial for efficient enzymatic production in the context of biorefinery.