Iskandaryan Meri, Blbulyan Syuzanna, Sahakyan Mayramik, Vassilian Anait, Trchounian Karen, Poladyan Anna
Department of Biochemistry, Microbiology, and Biotechnology, Biology Faculty, YSU, Yerevan, Armenia.
Research Institute of Biology, Biology Faculty, YSU, Yerevan, Armenia.
AMB Express. 2023 Mar 17;13(1):33. doi: 10.1186/s13568-023-01535-w.
Ralstonia eutropha H16 is a chemolithoautotrophic bacterium with O-tolerant hydrogenase (Hyds) enzymes. Hyds are expressed in the presence of gas mixtures (H, O, CO) or under energy limitation and stress conditions. O-tolerant Hyds are promising candidates as anode biocatalysts in enzymatic fuel cells (EFCs). Supplementation of 0.5% (w/v) yeast extract to the fructose-nitrogen (FN) growth medium enhanced H-oxidizing Hyd activity ~ sixfold. Our study aimed to identify key metabolites (L-amino acids (L-AAs) and vitamins) in yeast extract that are necessary for the increased synthesis and activity of Hyds. A decrease in pH and a reduction in ORP (from + 240 ± 5 mV to - 180 mV ± 10 mV values) after 24 h of growth in the presence of AAs were observed. Compared to the FN-medium control, supplementation of 7.0 μmol/ml of the L-AA mixture stimulated the growth of bacteria ~ 1.9 to 2.9 fold, after 72 h. The whole cells' H-oxidizing Hyd activity was not observed in control samples, whereas the addition of L-AAs, mainly glycine resulted in a maximum of ~ 22 ± 0.5 and 15 ± 0.3 U, g CDW activity after 24 h and 72 h, respectively. Our results suggest a correlation between ORP, pH, and function of Hyds in R. eutropha H16 in the presence of key L-AAs. L-AAs used in small amounts can be proposed as signaling molecules or key components of Hyd maturation. These results are important for the optimization of O-tolerant Hyds production as anode biocatalysts.
嗜麦芽窄食单胞菌H16是一种具有耐氧氢化酶（Hyds）的化能自养细菌。Hyds在气体混合物（H、O、CO）存在的情况下，或在能量限制和应激条件下表达。耐氧Hyds有望成为酶燃料电池（EFCs）中的阳极生物催化剂。在果糖-氮（FN）生长培养基中添加0.5%（w/v）酵母提取物可使H氧化Hyd活性提高约6倍。我们的研究旨在确定酵母提取物中对Hyds合成增加和活性增强所必需的关键代谢物（L-氨基酸（L-AAs）和维生素）。在存在氨基酸的情况下生长24小时后，观察到pH值下降和氧化还原电位降低（从+240±5 mV降至-180 mV±10 mV）。与FN培养基对照相比，添加7.0 μmol/ml的L-AA混合物在72小时后刺激细菌生长约1.9至2.9倍。对照样品中未观察到全细胞的H氧化Hyd活性，而添加L-AAs（主要是甘氨酸）分别在24小时和72小时后导致最大活性约为22±0.5和15±0.3 U/g CDW。我们的结果表明，在关键L-AAs存在的情况下，嗜麦芽窄食单胞菌H16中氧化还原电位、pH值与Hyds功能之间存在相关性。少量使用的L-AAs可被提议作为信号分子或Hyd成熟的关键成分。这些结果对于优化作为阳极生物催化剂的耐氧Hyds的生产具有重要意义。
