Cost-effective microbial enzyme production from agro-industrial waste

Abstract

This thesis investigates the valorization of agro-industrial by-products as sustainable carbon sources for microbial enzyme production, focusing on a comparative matrix of biocatalysts and substrates. Specifically, the study screened three Bacillus strains (B. subtilis, B. amyloliquefaciens, and Bacillus atrophaeus ) for extracellular alpha-amylase efficiency, while simultaneously evaluating cellulase induction profiles of Aspergillus niger grown on potato peel waste, wheat bran, and wheat straw. Following sodium hydroxide NaOH pretreatment of the lignocellulosic biomass, solid-state and submerged fermentation protocols were utilized, with crude enzyme yields quantified through dinitrosalicylic acid (DNS) colorimetric assays and rigorous spectrophotometric regression modeling. Experimental results demonstrate how bacterial strain selection modulates amylase expression and how the structural complexity of raw biomass regulates cellulase induction while bypassing carbon catabolite repression; ultimately, this research integrates a conceptual framework for downstream purification with a techno-economic feasibility analysis to establish a viable, closed-loop biorefinery model for converting abundant local waste into high- value industrial biocatalysts.