Baghdasaryan Lusine, Trchounian Karen, Sawers Gary, Poladyan Anna
Department of Biochemistry, Microbiology and Biotechnology, Faculty of Biology, Yerevan State University, 1 A. Manoogian Str, Yerevan, 0025, Armenia.
Scientific-Research Institute of Biology, Yerevan State University, 1 A. Manoogian Str, Yerevan, 0025, Armenia.
Appl Microbiol Biotechnol. 2025 Jun 14;109(1):146. doi: 10.1007/s00253-025-13535-w.
Lignocellulosic wine grape waste (WGW) is a cheap medium for Escherichia coli growth and H production. The current study investigated the effect of initial redox potential (oxidation-reduction potential (ORP)) on the growth, H production, ORP kinetics, and current generation of the E. coli BW25113 parental and a mutant strain optimized for hydrogen evolution when fermenting WGW (40 g L) hydrolysate. Bacteria were cultivated anaerobically on pre-treated WGW hydrolysate with dilutions ranging from undiluted to fourfold dilution, at pH 7.5. Notably, a twofold diluted medium, with pH adjustment using KHPO, exhibited reduced acidification, prolonged H production, and enhanced biomass formation (OD, 1.5). The addition of the redox reagent DL-dithiothreitol (DTT) was found to positively influence the H production of both the E. coli BW25113 parental and mutant strains. H production started after 24 h of growth, reaching a maximum yield of 5.10 ± 0.02 mmol/L in the wild type and 5.3 ± 0.02 mmol/L in the septuple mutant strain, persisting until the end of the stationary growth phase. The introduction of 3 mM DTT induced H production from the early-exponential phase, indicating that reducing conditions enhanced H production. Furthermore, we assessed the efficacy of using intact E. coli cells (1.5 mg cell dry weight) as anode catalyst in a bio-electrochemical fuel-cell system. Whole cells of the septuple mutant grown under reduced ORP conditions yielded the highest electrical potential, reaching up to 0.7 V. The results highlight the potential of modifying medium buffering capacity and ORP as a tool to improve biomass yield and H production during growth on WGW for biotechnological biocatalyst applications. KEY POINTS: • Grape pomace hydrolysate (GPH)'s pH positively impacts on biomass and H yield • GPH with reduced ORP enhanced H yield in bacterial early-exponential growth • GPH with reduced ORP facilitates microbial current generation in the system.
木质纤维素葡萄酒葡萄废渣（WGW）是用于大肠杆菌生长和产氢的廉价培养基。当前研究调查了初始氧化还原电位（ORP）对大肠杆菌BW25113亲本菌株以及为优化氢气产生而构建的突变菌株在发酵WGW（40 g/L）水解产物时的生长、产氢、ORP动力学和电流产生的影响。细菌在预处理的WGW水解产物上进行厌氧培养，稀释倍数从未稀释到四倍稀释，pH值为7.5。值得注意的是，使用KHPO调节pH值的两倍稀释培养基表现出酸化程度降低、产氢时间延长和生物量形成增加（OD值为1.5）。发现添加氧化还原试剂DL-二硫苏糖醇（DTT）对大肠杆菌BW25113亲本菌株和突变菌株的产氢均有积极影响。生长24小时后开始产氢，野生型的最大产氢量为5.10±0.02 mmol/L，七重突变菌株为5.3±0.02 mmol/L，产氢持续到稳定生长阶段结束。引入3 mM DTT可从指数生长期早期诱导产氢，表明还原条件增强了产氢。此外，我们评估了在生物电化学燃料电池系统中使用完整的大肠杆菌细胞（1.5 mg细胞干重）作为阳极催化剂的效果。在降低的ORP条件下生长的七重突变体全细胞产生的电势最高，可达0.7 V。结果突出了调节培养基缓冲能力和ORP作为一种工具在WGW生长过程中提高生物量产量和产氢以用于生物技术生物催化剂应用的潜力。要点：•葡萄皮渣水解产物（GPH）的pH值对生物量和产氢量有积极影响•ORP降低的GPH在细菌指数生长期早期提高产氢量•ORP降低的GPH促进系统中的微生物电流产生。
