A Streamlined Strategy for Biohydrogen Production with Halanaerobium hydrogeniformans, an Alkaliphilic Bacterium

Abstract

Biofuels are anticipated to enable a shift from fossil fuels for renewable transportation and manufacturing fuels, with biohydrogen considered attractive since it could offer the largest reduction of global carbon budgets. Currently, lignocellulosic biohydrogen production remains inefficient with pretreatments that are heavily fossil fuel-dependent. However, bacteria using alkali-treated biomass could streamline biofuel production while reducing costs and fossil fuel needs. An alkaliphilic bacterium, Halanaerobium hydrogeniformans, is described that is capable of biohydrogen production at levels rivaling neutrophilic strains, but at pH 11 and hypersaline conditions. H. hydrogeniformans ferments a variety of 5- and 6-carbon sugars derived from hemicellulose and cellulose including cellobiose, and forms the end products hydrogen, acetate, and formate. Further, it can also produce biohydrogen from switchgrass and straw pretreated at temperatures far lower than any previously reported and in solutions compatible with growth. Hence, this bacterium can potentially increase the efficiency and efficacy of biohydrogen production from renewable biomass resources.

Fermentative hydrogen production by a new alkaliphilic Clostridium sp. (strain PROH2) isolated from a shallow submarine hydrothermal chimney in Prony Bay, New Caledonia

“…Within this range, no optimum can be detected because no significant difference in both growth and H 2 production has been observed. Contrary to strain PROH2, which does not require NaCl for growth, most of H 2 -producing alkaliphilic strains, such H. hydrogeniformans [16], are considered as halophiles thus requiring NaCl for growth (>70 g/L). The unique physiological feature of strain PROH2 could result from the high pH and low salinity (<0.5 g/ L) existing in hydrothermal fluids released by the sampled chimney in the marine lagoon environment of Prony bay in New Caledonia [27].…”

“…Regarding alkaline culture conditions, Lee et al [18] reported an optimal initial pH of 9 for the batch H 2 fermentation of sucrose by mixed culture from a soybeanmeal silo. An alkaliphilic moderately halophilic bacterium, Haloanaerobium hydrogeniformans, isolated from Soap Lake (WA, USA) was also described as an efficient H 2 -producer at pH 11 rivaling neutrophilic strains [16]. In another study, fermentative H 2 production has been enhanced and stabilized by the alkaline pre-treatment of sewage sludge combined with a high initial pH [21,22].…”

“…In contrast, to our knowledge, fermentative H 2 production by other extremophiles, such as alkaliphiles (i.e., microorganisms growing optimally at pH values above 9), has been poorly studied [13,16]. The pH value is recognized as one of the key physicochemical factors affecting the H 2 production by fermentative bacteria [8,17e20].…”

“…Diverse extreme environments, such as hydrothermal vents or soda lakes, are potential sources for discovering novel fermentative H 2 -producing microorganisms [10,13,16]. Serpentization-driven ecosystems are characterized by high alkaline pH (10e12) and anoxic fluids with high concentrations of H 2 and methane [23].…”

Biotechnological application of microbial sulfidogenesis at haloalkaline conditions

“…In soda lakes, formate is mostly reported as a minor product of fermentation of more complex organic compounds while H2 is one of the major products (Zhilina et al 1996;Pikuta et al 2000;Zhilina et al 2005;Pikuta et al 2006;Pikuta et al 2009;Begemann et al 2012) . However, there are isolates, such as Amphibacillus fermentum and Amphibacillus tropicus, that produce formate as the major product from sugar fermentation .…”