Bioconversion of starch processing wastewater into bacterial cellulose for sandy soil remediation

Starch processing wastewater (SPW) is a high-strength organic effluent that imposes substantial treatment costs, while its high starch content also represents a potentially valuable carbon resource. Here, we developed an integrated waste-to-resource strategy for converting SPW into bacterial cellulose (BC) for sandy soil amelioration. To enable direct starch utilization, a strain capable of both amylase secretion and BC production was constructed. A sterilization-free fermentation process using raw SPW without an external carbon source was subsequently established and scaled from 120 mL to a 6 L working volume in a 10 L fermenter. Within 24 h, the process produced 871 ± 13 g/L wet SPW-derived BC (SPW-BC), while reducing wastewater volume, suspended solids, starch, and chemical oxygen demand by 87.17%, 98.09%, 84.60%, and 61.25%, respectively. When incorporated into sandy soil, SPW-BC improved soil water retention and aggregate stability, increasing water-stable macroaggregates from 11.97 ± 0.31% to 21.00 ± 0.36%, corresponding to a 75.4% increase relative to untreated soil. SPW-BC also enhanced soil nutrient availability and promoted lettuce growth, with the seedling vigor index reaching 0.69 ± 0.08. Overall, this study establishes a scalable platform that integrates SPW valorization, low-cost BC production, and sandy soil restoration, providing a promising route for coupling industrial wastewater management with sustainable land amelioration.