Use of Algae Biomass Obtained by Single-Step Mild Acid Hydrolysis in Hydrogen Production by the β-Glucosidase-Producing Clostridium beijerinckii Br21

Macroalgae biomass is a potential feedstock for fermentative H 2 production: it has high carbohydrate concentration and is lignin-free. Here, we optimize a mild acid treatment of Kappaphycus alvarezii biomass by an experimental design 2 4 . The optimal acid treatment conditions were 90 °C, HCl concentration of 55.9 mmol/L, 0.375 g of algae mass, and 8 h of treatment. Under these conditions, the hydrolysate presented mono-, but also di- and oligosaccharides. We used this hydrolysate as substrate for fermentative hydrogen (H 2 ) production by the Clostridium beijerinckii Br21 grown in two different conditions: (1) in medium containing galactose and no β-glucosidase activity; (2) in medium with cellobiose to stimulate β-glucosidase activity, which was 0.33U/mL. The fermentative assay conducted in the presence of the C. beijerinckii Br21 with β-glucosidase activity provided higher H 2 concentration and yield as compared to the assay accomplished in the presence of the inoculum with no β-glucosidase activity—171.76 ± 2.10 and 140.95 ± 10.92 mL of H 2 /L, and 70.3 ± 0.9 and 62.7 ± 4.9 mL of H 2 /g of dry algae, respectively. Therefore, a fermentative β-glucosidase-producing organism such as C. beijerinckii Br21 can potentially complete biomass saccharification for later renewable H 2 production.