Santos Ana Laura, Johnson D Barrie
School of Natural Sciences, Bangor University, Bangor, United Kingdom.
Life Sciences, Natural History Museum, London, United Kingdom.
Front Bioeng Biotechnol. 2022 Aug 11;10:937987. doi: 10.3389/fbioe.2022.937987. eCollection 2022.
Sulfate-reducing bacteria (SRB) catalyse the dissimilatory reduction of sulfate to hydrogen sulfide using a wide range of small molecular weight organic compounds, and hydrogen, as electron donors. Here we report the effects of different combinations of small molecular weight alcohols on the performance and bacterial composition of a moderately low pH sulfidogenic bioreactor (pH 4.0-5.5) operated at 35°C in continuous flow mode. Ethanol alone and methanol or ethanol used in combination with glycerol were evaluated based on their equivalent amounts of carbon. Although evidenced that methanol was utilised as electron donor to fuel sulfidogenesis at pH 5.5, rates of sulfate reduction/sulfide production were negatively impacted when this alcohol was first introduced to the system, though these rates increased in subsequent phases as a result of adaptation of the microbial community. Further increased dosage of methanol again caused rates of sulfidogenesis to decrease. Methanol addition resulted in perturbations of the bioreactor microbial community, and species not previously detected were present in relatively large abundance, including the sulfate-reducer . Ethanol utilization was evidenced by the increase in rates of sulfidogenesis as the dosage of ethanol increased, with rates being highest when the bioreactor was fed with ethanol alone. Concentrations of acetate in the effluent liquor also increased (up to 8 mM) as a result of incomplete oxidation of ethanol. This alcohol continued to be used as the electron donor for sulfate reduction when the bioreactor pH was decreased incrementally (to pH 4.0), but rates of sulfidogenesis decreased. The relative abundance of diminished as the bioreactor pH was lowered, while that of the acidophilic increased. This study has shown that all three alcohols can be used to fuel microbial sulfidogenesis in moderately acidic liquors, though the cost-effectiveness, availability and toxicity to the microbial community will dictate the choice of substrate.
硫酸盐还原菌（SRB）利用多种小分子有机化合物和氢气作为电子供体，将硫酸盐异化还原为硫化氢。在此，我们报告了小分子醇类不同组合对一个在35°C下以连续流模式运行的中等低pH值产硫化物生物反应器（pH 4.0 - 5.5）的性能和细菌组成的影响。基于等碳量对单独的乙醇以及甲醇或乙醇与甘油组合使用的情况进行了评估。虽然已证明甲醇在pH 5.5时可作为电子供体促进硫化物生成，但当该醇首次引入系统时，硫酸盐还原/硫化物生成速率受到负面影响，不过由于微生物群落的适应，这些速率在后续阶段有所增加。再次增加甲醇剂量又导致硫化物生成速率下降。添加甲醇导致生物反应器微生物群落受到扰动，并且出现了以前未检测到的物种，其丰度相对较高，包括硫酸盐还原菌。随着乙醇剂量增加，硫化物生成速率提高，这证明了乙醇的利用情况，当生物反应器单独进料乙醇时速率最高。由于乙醇不完全氧化，流出液中乙酸盐浓度也增加（高达8 mM）。当生物反应器pH值逐渐降低至pH 4.0时，这种醇继续用作硫酸盐还原的电子供体，但硫化物生成速率下降。随着生物反应器pH值降低， 的相对丰度下降，而嗜酸 的相对丰度增加。这项研究表明，所有三种醇都可用于促进中等酸性溶液中的微生物硫化物生成，不过成本效益、可用性以及对微生物群落的毒性将决定底物的选择。
