Integrating enzyme production and bioenergy recovery through circular bioprocessing of carbohydrate‐rich food wastes into <i>α</i> ‐amylase, hydrogen and methane

Abstract This study explored the valorization of two carbohydrate rich food wastes, a sugary (spoiled dates, SD) and a starchy (wasted rice, WR) one, for the biotechnological production of α ‐amylase, biohydrogen (bioH 2 ), and methane (CH 4 ). Initially, the bioH 2 and CH 4 production potentials of raw SD and WR were assessed without any pretreatment, via dark fermentation and anaerobic digestion, respectively, to evaluate the need of sacharification of the wastes for achieving efficient yields. For the production of amylolytic enzymes the bacterium Bacillus amyloliquefaciens was used. Aerobic experiments with synthetic media were initially performed to evaluate the effect of carbon and nitrogen sources on microbial growth, substrate uptake and stimulation of α ‐amylase production. Subsequently a mixture of the SD and WR, supplemented with peptone, was used as a substrate for α ‐amylase production, achieving a maximum enzymatic activity of 35.7 ± 1.1 AU mL −1 . The impact of enzymatic and acid saccharification on biofuel production was then evaluated using commercial α ‐amylases, crude α ‐amylase produced in situ by B. amyloliquefaciens , and HCl. Commercial enzymes maximized bioH 2 yields, while crude α ‐amylase also enhanced production considerably. HCl pretreatment improved WR conversion but reduced bioH 2 yields from SD. Saccharification showed only a limited effect on CH 4 production, with no statistically significant improvements over untreated WR. Overall, SD and WR show strong potential as zero‐cost feedstocks for α ‐amylase and gaseous biofuel production, supporting circular economy principles. Valorization of these carbohydrate‐rich wastes could reduce feedstock costs and provide a sustainable approach to enzyme and bioenergy generation.