Sustainable Valorization of Organic Waste Via α-Amylase-Mediated Biocatalysis: A Green Bioprocessing Strategy

The increasing environmental impact of food waste, especially starch-rich residues, necessitates sustainable biodegradation methods to reduce pollution and resource wastage.

This study aimed to isolate α-amylase-producing bacteria from saline-rich organic soils in Jeddah, Saudi Arabia, and assess their effectiveness in degrading food waste through enzymatic starch hydrolysis.

Twenty bacterial isolates were screened on starch agar for amylolytic activity. The most productive strain, Bacillus subtilis A16, was identified using biochemical assays (Gram staining, catalase/oxidase tests) and 16S rRNA sequencing. Enzyme production was optimized at different pH levels (4-9) and temperatures (30-60 °C). Purification involved ammonium sulfate precipitation (80% saturation), dialysis, and chromatography (Sephadex G-100, DEAE-Sephadex A-50). The purified enzyme was applied to 10 kg of food waste (bread and fruits) to evaluate degradation efficiency.

B. subtilis A16 exhibited the highest α-amylase activity (1.467 U. mL^-1) with optimal performance at pH 8 (0.588 U. mL^-1) and 40 °C (1.386 U.mL^-1). Purification resulted in a 58 kDa enzyme with a 3.7-fold increase in specific activity (5.448 U.mg-1). Food waste treated with AK16 showed a 50% volume reduction within 25 days, accompanied by rapid starch decomposition.

The study highlights B. subtilis A16 as a highly effective and environmentally friendly biocatalyst for the degradation of starch-rich waste. Its excellent alkaline and thermal stability, along with its ability to efficiently reduce waste, demonstrate its potential for sustainable use in industrial and environmental settings. These results present a promising bio-based approach to managing organic waste, promoting a circular economy, and minimizing the environmental impact of waste disposal.