Isolation and characterization of a hydrogen- and ethanol-producing Clostridium sp. strain URNW

Abstract

Identification, characterization, and end-product synthesis patterns were analyzed in a newly identified mesophilic, anaerobic Clostridium sp. strain URNW, capable of producing hydrogen (H₂) and ethanol. Metabolic profiling was used to characterize putative end-product synthesis pathways of the Clostridium sp. strain URNW, which was found to grow on cellobiose; on hexose sugars, such as glucose, sucrose, and mannose; and on sugar alcohols, like mannitol and sorbitol. When grown in batch cultures on 2 g cellobiose·L⁻¹, Clostridium sp. strain URNW showed a cell generation time of 1.5 h, and the major end-products were H2, formate, carbon dioxide (CO₂), lactate, butyrate, acetate, pyruvate, and ethanol. The total volumetric H₂ production was 14.2 mmol·(L culture)⁻¹ and the total production of ethanol was 0.4 mmol·(L culture)⁻¹. The maximum yield of H₂ was 1.3 mol·(mol glucose equivalent)⁻¹ at a carbon recovery of 94%. The specific production rates of H₂, CO₂, and ethanol were 0.45, 0.13, and 0.003 mol·h⁻¹·(g dry cell mass)-1, respectively. BLAST analyses of 16S rDNA and chaperonin 60 (cpn60) sequences from Clostridium sp. strain URNW revealed a 98% nucleotide sequence identity with the 16S rDNA and cpn60 sequences from Clostridium intestinale ATCC 49213. Phylogenetic analyses placed Clostridium sp. strain URNW within the butyrate-synthesizing clostridia.