<b>Dark Fermentative Hydrogen Production from Dilute Acid Pre-treated Paddy Straw Using <i>Enterobacter aerogenes</i></b>

Paddy straw is a promising alternative resource for biohydrogen production as it is abundant, cheap, renewable and biodegradable. The physicochemical treatments such as dilute acid pre-treatment helps to disrupt its recalcitrant structure and solubilize the complex carbohydrates into sugars for the dark fermentation process. The present study assessed the fermentative hydrogen production from the sugars released by acid pre-treatment of paddy straw. The treatment of straw with acidic solution (2% sulphuric acid) at a solid-liquid ratio of 1:5 for 60 min resulted in the release of maximum amount of reducing sugars, yielding 11.77 g L⁻¹ in the hydrolysate. Dark fermentation of sugar-rich hydrolysate by the facultative anaerobe Enterobacter aerogenes at different initial pH levels resulted in significant variations in the gas production. At the optimum hydrolysate pH of 5.5, maximum cumulative hydrogen production, yield, and sugar utilization of 331.29 mL L⁻¹, 0.25 mol H₂ mol⁻¹ sugar, and 95.85%, respectively, were achieved after 72 h of fermentation. These findings highlight the potential of sugar-rich liquid fraction generated during dilute acid pretreatment of paddy straw for dark fermentative hydrogen production, offering a promising route for the valorization of hemicellulosic sugars into clean energy.