Screening of Clostridium sp. For biohydrogen production from synthetic wastewater

Abstract

In this work, bacteria that can produce endospores were isolated from natural sources and industrial wastes, including mangrove forests, hot springs, and coconut factories. The bacterial isolates were identified as Clostridium spp. and Panibacillus spp. based on 16S RNA gene. When comparing the H2 produced by batch fermentation, two of the isolates with the best H2 production were selected for further study, namely CUEA01 and CUEA03. After genomics analysis, it was discovered that CUEA01 is a novel species named C. hydrogenum, and CUEA03 is C. felsineum. Both are capable of growing and producing H2 in alkaline conditions. The genomics data reveal that they contain genetic information capable of encoding a variety of enzymes that aid in the process of H2 production and also carbon source utilization. Following optimization of the H2 production conditions for the two species, it was discovered that CUEA01 produced the highest cumulative H2 yield of 3264 mL/L (3.11 molH2/molglucose) at 37 °C, pH 8, and 10 g/L of the initial carbon source, while CUEA03 is 5425 mL/L (1.70 molH2/molglucose) at 72 h of incubation was obtained from an initial glucose concentration of 35 g/L, pH 9, and an incubation temperature of 30 °C. Furthermore, different carbon sources were used as substrates to evaluate their feasibility of usage, and the results demonstrated that these species could secrete an effective enzyme capable of digesting various carbon sources to produce H2 gas. Moreover, industrial by-products and agricultural residues have been employed as feedstocks to produce H2 instead of simple sugar. It was found that CUEA01 was able to produce H2 from the three wastes and was able to produce H2 at an amount of 4639 mL/L from molasses and 4024 mL/L from cassava pulp, while CUEA03 could produce 5187 mL/L from molasses. Thus, this study indicates that both microorganisms have the potential to be used to produce H2 from organic wastes, which will help integrate bioprocesses into waste treatment and clean energy production, which can help fulfill future fuel generation goals.