Evaluation of low cost immobilized support matrices in augmentation of biohydrogen potential in dark fermentation process using B. licheniformis AP1

• Support carriers were optimized for biohydrogen augmentation. • Cell adsorption method is highly efficient in comparison to cell entrapment. • Foam was the best carrier for higher cell density adsorption. • The highest biohydrogen production was reported as 138 mL/30 mL using foam carrier. • The highest hydrogen yield was achieved as 2.07 mol/mol of glucose using a foam carrier. In this study, the impact of immobilized (cell adsorbed and cell entrapped) matrices or beads on biohydrogen production potential has been reported. The novelty of this research is to investigate the impact of natural waste matrices or carriers (coconut coir-CC, wood shaving-WS) and low cost carriers (foam-FM, and alginate) on biohydrogen production potential. The study for dark fermentation process was performed for 2 days with four batch tests using cell adsorption method and six batch tests using cell entrapment method at initial pH (6.5), and temperature 38 ± 2 °C temperature. Cell adsorbed solid matrices reported maximum biohydrogen potential results as 62 ± 5.6 mL H 2 /30 mL (control), 138 mL ± 7 mL H 2 /30 mL (foam), 103.75 ± 6.7 mL H 2 /30 mL (coconut coir), and 96 ± 6.36 mL H 2 /30 mL (wood shaving). In cell entrapment, alginate supplemented TiO 2 -NP reported results as 32 mL ± 2.8/30 mL (control- 0 TiO 2 mg/L), 35 ± 2.4 mL/30 mL (200 TiO 2 mg/L), 40 ± 2.8 mL/30 mL (400 TiO 2 mg/L), 53 ± 4 mL/30 mL (600 TiO 2 mg/L), 75 ± 4.2 mL/30 mL (800 TiO 2 mg/L), and 93 ± 3 mL/30 mL (1000 TiO 2 mg/L) respectively. The SEM observation displayed that foam was the best carrier for high cell adhesion on its surface in comparison to other carriers due to surface characteristics. The current study achieved maximum yield 2.07 mol/mol of glucose using foam carrier. Majorly, acetic acid followed by butyric acid is analyzed as by-products at the end of dark fermentation.