Sustainable biohydrogen production from banana peels using microbial fermentation

BACKGROUND: Global energy demand and environmental concerns are driving the search for sustainable alternatives. Banana peels, which account for 30–40% of the 139 million tons of bananas produced annually, are rich in organic matter and offer a promising source for biofuel production. To investigate this potential, experiments were conducted to assess their suitability for biofuel generation. METHODS: Microbial conversion of banana peels into hydrogen and acetone-butanol-ethanol (ABE) was investigated through anaerobic fermentation and enzymatic hydrolysis. Various inocula were tested for anaerobic digestion. Peels concentration kinetics were analyzed, and bacterial isolates were screened for their ability to degrade phenolic compounds, produce cellulase and pectinase, and generate biofuels. The most efficient isolate was identified using 16 S rRNA sequencing. RESULTS: Findings demonstrate that banana peels have a high volatile solids content of 93.7%, a rich carbohydrate profile (550 mg/g reducing sugars, 133.25 mg/g total carbohydrates), and a balanced C/N ratio of 21.5, making them a promising substrate for biofuel production and waste management. In evaluating inoculum performance, chicken manure proved to be the most effective inoculum, producing 846.6 mL/L of hydrogen with a bacterial count of 12.67 × 10⁵ CFU/mL, followed by cow dung (283.3 mL/L of hydrogen). Soil inoculum did not result in hydrogen production despite microbial activity. Furthermore, the optimal hydrogen production was achieved at a 20% (w/v) banana peels concentration, reaching 1400 mL/L, with higher concentrations (40%) showing inhibition. The Gompertz model confirmed the peak performance at 20% concentration (Hₘₐₓ = 1330 mL, Rₘₐₓ = 130 mL/h, R² = 0.99). Among bacterial isolates, isolate W26 (Bacillus stercoris, 99.93% 16 S rRNA identity) from cow rumen produced the highest hydrogen (1750 mL/L), while W17 excelled in ABE production (1.033 g/L, primarily ethanol). Bacterial isolates W17, W18 and W22 demonstrated cellulase activity, while W13, W20, W23 and W24 exhibited pectinase activity, with W26 showing both. Tolerance to phenolic compounds varied among isolates, with gallic acid, ferulic acid, quercetin, and tannic acid supporting growth in most isolates, unlike pyrogallol. Collectively, these findings highlight the potential of banana peels for sustainable biofuel production, with chicken manure and Bacillus stercoris as the optimal inoculum and isolate, respectively. CONCLUSIONS: Based on these findings, banana peels are a promising biofuel substrate due to their high carbohydrate content and favorable C/N ratio. Chicken manure and bacterial isolate W26 (Bacillus stercoris) were found to boost hydrogen production at a 20% peels concentration, yielding 1400 mL/L and 1750 mL/L, respectively. Some isolates exhibited cellulase, pectinase, and ABE production capabilities, with W17 achieving the highest ethanol yield of 0.930 g/L. These results highlight the viability of banana peels for eco-friendly bioenergy production and effective waste management.