Jifei Xu

Bioconversion of lignocellulosic biomass to hydrogen: Potential and challenges.

No comprehensive review on the bioconversion of lignocellulosic biomass to hydrogen is presented. This paper provides an up-to-date review on recent research development in biotechnology-based lignocellulosic biomass-to-H(2) conversion. Bioconversion of lignocellulosic prehydrolysate, hydrolysate or cellulose to hydrogen was discussed in terms of the involved microorganisms and the bioaugmentation tactics. To achieve fully the utilization of biomass, the integrated approaches composed of coupled dark-photo fermentation and the dark fermentation and bioelectrohydrogenesis were sketched. Additionally, this review sheds light on the perspectives on the lignocellulosic biomass conversion to hydrogen, and on the scientific and technical challenges faced for the lignocelluloses bioconversion.

Hydrogen production by immobilized R. faecalis RLD-53 using soluble metabolites from ethanol fermentation bacteria E. harbinense B49

In order to increase the hydrogen yield from glucose, hydrogen production by immobilized Rhodopseudomonas faecalis RLD-53 using soluble metabolites from ethanol fermentation bacteria Ethanoligenens harbinense B49 was investigated. The soluble metabolites from dark-fermentation mainly were ethanol and acetate, which could be further utilized for photo-hydrogen production. Hydrogen production by B49 was noticeably affected by the glucose and phosphate buffer concentration. The maximum hydrogen yield (1.83 mol H(2)/mol glucose) was obtained at 9 g/l glucose. In addition, we found that the ratio of acetate/ethanol (A/E) increased with increasing phosphate buffer concentration, which is favorable to further photo-hydrogen production. The total hydrogen yield during dark- and photo-fermentation reached its maximum value (6.32 mol H(2)/mol glucose) using 9 g/l glucose, 30 mmol/l phosphate buffers and immobilized R. faecalis RLD-53. Results demonstrated that the combination of dark- and photo- fermentation was an effective and efficient process to improve hydrogen yield from a single substrate.

Isolation and characterization of Shigella flexneri G3, capable of effective cellulosic saccharification under mesophilic conditions.

ABSTRACT A novel Shigella strain (Shigella flexneri G3) showing high cellulolytic activity under mesophilic, anaerobic conditions was isolated and characterized. The bacterium is Gram negative, short rod shaped, and nonmotile and displays effective production of glucose, cellobiose, and other oligosaccharides from cellulose (Avicel PH-101) under optimal conditions (40°C and pH 6.5). Approximately 75% of the cellulose was hydrolyzed in modified ATCC 1191 medium containing 0.3% cellulose, and the oligosaccharide production yield and specific production rate reached 375 mg g Avicel−1 and 6.25 mg g Avicel−1 h−1, respectively, after a 60-hour incubation. To our knowledge, this represents the highest oligosaccharide yield and specific rate from cellulose for mesophilic bacterial monocultures reported so far. The results demonstrate that S. flexneri G3 is capable of rapid conversion of cellulose to oligosaccharides, with potential biofuel applications under mesophilic conditions.