“…However, in the last decade, biological processes employing bacteria for H 2 production have received a significant and increasing attention [2–11]. Indeed, like with other biofuels such as ethanol, butanol, fatty acids, and methane, bio-hydrogen can be produced by processes using living organisms such as green algae (photolysis of water), phototrophic and anaerobic microorganisms (photofermentation of organic acids), and anaerobic fermentative microorganisms (dark fermentation of organic substrates) [2, 7, 8, 11–19]. Among these, due to the large spectrum of catabolic activities of H 2 -producing microorganisms, dark fermentation is considered as one of the most promising route.…”
Background
Thermotoga maritima and T. neapolitana are hyperthermophile bacteria chosen by many research teams to produce bio-hydrogen because of their potential to ferment a wide variety of sugars with the highest theoretical H2/glucose yields. However, to develop economically sustainable bio-processes, the culture medium formulation remained to be optimized. The main aim of this study was to quantify accurately and specifically the effect of thiosulfate, used as sulfured nutriment model, on T. maritima growth, yields and productivities of hydrogen. The results were obtained from batch cultures, performed into a bioreactor, carefully controlled, and specifically designed to prevent the back-inhibition by hydrogen.ResultsAmong sulfured nutriments tested, thiosulfate, cysteine, and sulfide were found to be the most efficient to stimulate T. maritima growth and hydrogen production. In particular, under our experimental conditions (glucose 60 mmol L−1 and yeast extract 1 g L−1), the cellular growth was limited by thiosulfate concentrations lower than 0.06 mmol L−1. Under these conditions, the cellular yield on thiosulfate (Y X/Thio) could be determined at 3617 mg mmol−1. In addition, it has been shown that the limitations of T. maritima growth by thiosulfate lead to metabolic stress marked by a significant metabolic shift of glucose towards the production of extracellular polysaccharides (EPS). Finally, it has been estimated that the presence of thiosulfate in the T. maritima culture medium significantly increased the cellular and hydrogen productivities by a factor 6 without detectable sulfide production.ConclusionsThe stimulant effects of thiosulfate at very low concentrations on T. maritima growth have forced us to reconsider its role in this species and more probably also in all thiosulfato-reducer hyperthermophiles. Henceforth, thiosulfate should be considered in T. maritima as (1) an essential sulfur source for cellular materials when it is present at low concentrations (about 0.3 mmol g−1 of cells), and (2) as both sulfur source and detoxifying agent for H2 when thiosulfate is present at higher concentrations and, when, simultaneously, the pH2 is high. Finally, to improve the hydrogen production in bio-processes using Thermotoga species, it should be recommended to incorporate thiosulfate in the culture medium.
“…However, in the last decade, biological processes employing bacteria for H 2 production have received a significant and increasing attention [2–11]. Indeed, like with other biofuels such as ethanol, butanol, fatty acids, and methane, bio-hydrogen can be produced by processes using living organisms such as green algae (photolysis of water), phototrophic and anaerobic microorganisms (photofermentation of organic acids), and anaerobic fermentative microorganisms (dark fermentation of organic substrates) [2, 7, 8, 11–19]. Among these, due to the large spectrum of catabolic activities of H 2 -producing microorganisms, dark fermentation is considered as one of the most promising route.…”
Background
Thermotoga maritima and T. neapolitana are hyperthermophile bacteria chosen by many research teams to produce bio-hydrogen because of their potential to ferment a wide variety of sugars with the highest theoretical H2/glucose yields. However, to develop economically sustainable bio-processes, the culture medium formulation remained to be optimized. The main aim of this study was to quantify accurately and specifically the effect of thiosulfate, used as sulfured nutriment model, on T. maritima growth, yields and productivities of hydrogen. The results were obtained from batch cultures, performed into a bioreactor, carefully controlled, and specifically designed to prevent the back-inhibition by hydrogen.ResultsAmong sulfured nutriments tested, thiosulfate, cysteine, and sulfide were found to be the most efficient to stimulate T. maritima growth and hydrogen production. In particular, under our experimental conditions (glucose 60 mmol L−1 and yeast extract 1 g L−1), the cellular growth was limited by thiosulfate concentrations lower than 0.06 mmol L−1. Under these conditions, the cellular yield on thiosulfate (Y X/Thio) could be determined at 3617 mg mmol−1. In addition, it has been shown that the limitations of T. maritima growth by thiosulfate lead to metabolic stress marked by a significant metabolic shift of glucose towards the production of extracellular polysaccharides (EPS). Finally, it has been estimated that the presence of thiosulfate in the T. maritima culture medium significantly increased the cellular and hydrogen productivities by a factor 6 without detectable sulfide production.ConclusionsThe stimulant effects of thiosulfate at very low concentrations on T. maritima growth have forced us to reconsider its role in this species and more probably also in all thiosulfato-reducer hyperthermophiles. Henceforth, thiosulfate should be considered in T. maritima as (1) an essential sulfur source for cellular materials when it is present at low concentrations (about 0.3 mmol g−1 of cells), and (2) as both sulfur source and detoxifying agent for H2 when thiosulfate is present at higher concentrations and, when, simultaneously, the pH2 is high. Finally, to improve the hydrogen production in bio-processes using Thermotoga species, it should be recommended to incorporate thiosulfate in the culture medium.
“…With glucose used as the substrate, the hydrogen yield of MJ1was much higher than that of W16, PSU-2 and TERI S7 [8, 19, 28], proving that glucose can be well utilized by MJ1 and is suitable for hydrogen production. Li et al [2] and Ren et al [7] have proposed strategies for hydrogen production from lignocellulose by T. thermosaccharolyticum which lacks the ability to degrade lignocellulose, implying that MJ1 is a good candidate for hydrogen production.Fig. 2Hydrogen production and metabolite production via strain MJ1 with different sugars.…”
BackgroundEnergy shortage and environmental pollution are two severe global problems, and biological hydrogen production from lignocellulose shows great potential as a promising alternative biofuel to replace the fossil fuels. Currently, most studies on hydrogen production from lignocellulose concentrate on cellulolytic microbe, pretreatment method, process optimization and development of new raw materials. Due to no effective approaches to relieve the inhibiting effect of inhibitors, the acid pretreated lignocellulose hydrolysate was directly discarded and caused environmental problems, suggesting that isolation of inhibitor-tolerant strains may facilitate the utilization of acid pretreated lignocellulose hydrolysate.ResultsThermophilic bacteria for producing hydrogen from various kinds of sugars were screened, and the new strain named MJ1 was isolated from paper sludge, with 99% identity to Thermoanaerobacterium thermosaccharolyticum by 16S rRNA gene analysis. The hydrogen yields of 11.18, 4.25 and 2.15 mol-H2/mol sugar can be reached at an initial concentration of 5 g/L cellobiose, glucose and xylose, respectively. The main metabolites were acetate and butyrate. More important, MJ1 had an excellent tolerance to inhibitors of dilute-acid (1%, g/v) pretreated sugarcane bagasse hydrolysate (DAPSBH) and could efficiently utilize DAPSBH for hydrogen production without detoxication, with a production higher than that of pure sugars. The hydrogen could be quickly produced with the maximum hydrogen production reached at 24 h. The hydrogen production reached 39.64, 105.42, 111.75 and 110.44 mM at 20, 40, 60 and 80% of DAPSBH, respectively. Supplementation of CaCO3 enhanced the hydrogen production by 21.32% versus the control.ConclusionsThese results demonstrate that MJ1 could directly utilize DAPSBH for biohydrogen production without detoxication and can serve as an excellent candidate for industrialization of hydrogen production from DAPSBH. The results also suggest that isolating unique strains from a particular environment offers an ideal way to conquer the related problems.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-017-0692-y) contains supplementary material, which is available to authorized users.
“…Fermentation of hydrolysates from Miscanthus hydrolysates by Caldicellulosiruptor saccharolyticus and Thermotoga elfi, pretreated by alkali, resulted in 3.4 and 3.2 mol H 2 mol glucose -1 equivalent, respectively (de Vrije et al, 2009). Corn stover and corn stover cornstalk have been investigated for H 2 production capacity by many Datar et al, 2007;Liu et al, 2008b;Liu & Cheng, 2010;Ren et al, 2010). Pure culture studies on Thermoanaerobacterium thermosaccharolyticum on corn stover hydrolysates showed maximum of 2.7 mol H 2 mol glucose -1 equivalent diluted corn stover hydrolysates that contained a mixture of glucose, xylose and arabinose (total sugar concentration, 10 g L -1 ) .…”
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