Magnetic Halloysite Nanotube/α-Amylase Based Nanobiocatalytic Transformation of Food Processing Waste into an Active Fermentation Ingredient
Devendra Sillu, Shekhar Agnihotri, S. M. Reddy
Abstract
The concept of “nanobiocatalysis” creates exciting opportunities for improving enzyme performance via immobilization onto nanomaterials. A nanobiocatalyst consisting of magnetic halloysite nanotube (MHNT)/α-amylase was evaluated to transform food processing waste into an active fermentation medium formulation for low-cost bioprocessing. A high loading of α-amylase (185.5 mg (g of support)−1) was achieved on the surface of MHNTs through polydopamine functionalization. We validated the establishment of an enzyme-support system retaining >89% catalytic activity (27332 IU (g of support)−1) with improved enzyme handling (>99.1% recovery) and reusability (>56% activity, 10 cycles). MHNTs remarkably improved the enzyme kinetics and thermodynamic characteristics along with operational and storage stabilities and mitigated the likely inhibitory effects of cellulose/metal ions as contaminants. In addition to facilitating a continuous production of reducing sugars from the extracted starch over 72 h, the nanobiocatalyst was equally effective in preparing a nutritive food waste hydrolysate as a fermentable medium substitute for batch culturing of E. coli and a single-cell protein (A. niger). The commercial relevance of waste hydrolysate was also investigated to promote calcite precipitation via Bacillus sp. induced biocementation. We evidenced that nanobiocatalyst-assisted “starch depolymerization” released more nutritional components into the hydrolysate suspension, easily accessible to growing microbial cultures.