Alkalibaculum bacchi gen. nov., sp. nov., a CO-oxidizing, ethanol-producing acetogen isolated from livestock-impacted soil

Abstract

Alkalibaculum bacchi gen. nov., sp. nov., a CO-oxidizing, ethanol-producing acetogen isolated from livestock-impacted soil Phenotypic and phylogenetic studies were performed on three strains of an acetogenic bacterium isolated from livestock-impacted soil. The bacterium stained Gram-negative and was a nonspore-forming rod that was motile by peritrichous flagella. The novel strains had an optimum pH for growth of 8.0-8.5 and utilized H 2 : CO 2 , CO : CO 2 , glucose, fructose, mannose, turanose, ribose, trimethylamine, pyruvate, methanol, ethanol, n-propanol and n-butanol as growth substrates. Acetate was produced from glucose. Acetate, CO 2 and ethanol were produced from CO : CO 2 . 16S rRNA gene sequence analysis indicated that the novel strains formed a new subline in the family Eubacteriaceae (rRNA cluster XV) of the low G+C-containing Gram-positive bacteria of the class Clostridia. The DNA G+C base composition was 34 mol%. Cell wall analysis revealed the existence of a novel B-type peptidoglycan similar to the B2a-type (B4) configuration with a variation containing aspartic acid. Based on phylogenetic and phenotypic evidence, it is proposed that the new isolates represent a novel genus and species, for which the name Alkalibaculum bacchi gen. nov., sp. nov. is proposed. The type strain of the type species is CP11 T (5ATCC BAA-1772Biological ethanol (bioethanol) production has captured worldwide attention as a result of fluctuating oil prices as well as 'green' initiatives to displace petroleum and lower CO 2 emissions. Most bioethanol produced in the USA is derived from the fermentation of corn starch. The result of increasing bioethanol production is thus direct competition with a food commodity and so this source is not viewed as a long-term sustainable option (Pimentel, 2003). Cellulosic ethanol production is a desirable alternative but current technologies have not overcome the obstacles (e.g. pretreatment and waste disposal) associated with the direct fermentation of cellulosic material (Lynd et al., 2008). An alternative to direct fermentation is the indirect fermentation of lignocellulosic biomass to ethanol. Using this method, biomass (e.g. switchgrass, corn stover, etc.) is pyrolysed to produce synthesis gas (CO : CO 2 : H 2 ) (McKendry, 2002;van der Drift et al., 2001). Some acetogenic bacteria can convert the synthesis gas to ethanol through anaerobic fermentation (Datar et al., 2004). Phylogenetically, acetogens are a diverse group of organisms within the Gram-positive, low G+C Clostridia, of which representative micro-organisms are found in eight of 19 Clostridium clusters (I, V, VI, IX, XI, XII, XIVa and XV) (Collins et al., 1994;Drake et al., 2006).However, while indirect fermentation of biomass by acetogens is an attractive option for bioethanol production, relatively few micro-organisms are known that can convert synthesis gas to ethanol . Of the most promising acetogens to date, Clostridium ljungdahlii, Clostridium carboxidivorans and a micro-organism also isolated in our laboratory, Clostr...

Methylotrophic methanogenesis governs the biogenic coal bed methane formation in Eastern Ordos Basin, China

“…Various relatives of the fermentative bacteria detected in our library were related to acetogens or facultative acetogens using H 2 as an electron donor such as clones related to Acetobacterium (Krumholz et al 1999;Paarup et al 2006), Alkalibaculum (Allen et al 2010), and Desulfosporosinus (Ramamoorthy et al 2006). The presence of acetogens might explain the non-detection of hydrogenotrophic methanogens.…”

Commercial Biomass Syngas Fermentation

“…bacchi was isolated from livestock-impacted soil in 2010 and has been recently investigated for the production of ethanol from syngas, with a reported ideal growth temperature of 37 °C [165]. This was notably carried out at an initial pH between 7.7 and 8.0, with A. bacchi moderately alkaliphilic [166].…”

Influences of pH Conditions on Syngas Fermentation using Clostridium ljungdahlii

“…This bacterium has the similar characteristics as Clostridium ljungdahlii. Then more bac-terium were discovered they can converse syngas to ethanol and acetate including Clostridium autoethanogenum (Abrini, Naveau et al, 1994), Clostridium ragsdalei (P11) (Kundiyana, Huhnke et al, 2010), Butyribacterium methylotrophicum (Grethlein, Worden et al, 1991) and Alkalibaculum bacchi (Allen, Caldwell et al, 2010). These bacterium require similar pH and temperature environments.…”