Analysis of the key enzymes of butyric and acetic acid fermentation in biogas reactors

Abstract

This study aimed at the investigation of the mechanisms of acidogenesis, which is a key process during anaerobic digestion. To expose possible bottlenecks, specific activities of the key enzymes of acidification, such as acetate kinase (Ack, 0.23–0.99 U mg−1 protein), butyrate kinase (Buk, < 0.03 U mg−1 protein) and butyryl-CoA:acetate-CoA transferase (But, 3.24–7.64 U mg−1 protein), were determined in cell free extracts of biogas reactor content from three different biogas reactors. Furthermore, the detection of Ack was successful via Western blot analysis. Quantification of corresponding functional genes encoding Buk (buk) and But (but) was not feasible, although an amplification was possible. Thus, phylogenetic trees were constructed based on respective gene fragments. Four new clades of possible butyrate-producing bacteria were postulated, as well as bacteria of the genera Roseburia or Clostridium identified. The low Buk activity was in contrast to the high specific But activity in the analysed samples. Butyrate formation via Buk activity does barely occur in the investigated biogas reactor. Specific enzyme activities (Ack, Buk and But) in samples drawn from three different biogas reactors correlated with ammonia and ammonium concentrations (NH3 and NH4+-N), and a negative dependency can be postulated. Thus, high concentrations of NH3 and NH4+-N may lead to a bottleneck in acidogenesis due to decreased specific acidogenic enzyme activities.

Enhanced methane production through bioaugmentation of butyrate‐oxidizing hydrogen‐producing acetogens in anaerobic wastewater treatment

“…Consequently, it is possible to assert that the relatively high methane production may also be achieved by the inoculation and bioaugmentation of butyrate-oxidizing HPAs [21]. Furthermore, butyric acid can be fermented during anaerobic wastewater treatment [4,22,23], and the terminal products become extensively diverse [24][25][26]. Degradation of butyric acid by HPAs occurs considerably more easily than that of propionic acid; thus, in this work, a microflora dominated by HPAs that oxidize butyric acid was obtained by subculture of anaerobic sludge, and the efficiency of this microflora in enhancing methane production and anaerobic organic wastewater treatment was evaluated.…”

Genome Sequence of Lactobacillus sunkii Strain CG_D

“…Additionally, 16S rRNA gene sequences of the genus Lactobacillus were found in microbial communities of biogas reactors (3, 4). Here, we present the draft genome sequence of the L. sunkii CG_D strain, which was isolated from biogas reactor content and initially designated L. sunkii CG01 (5). The biogas reactor was fed with maize silage and cattle and poultry dry manure and is located in Troisdorf, Germany (6).…”

“…We also identified genes encoding phosphotransacetylase and acetate kinase as well as several genes encoding alcohol dehydrogenase and l -lactate dehydrogenase. Moreover, growth experiments showed acetic acid, lactic acid, and ethanol production (5). …”

Genome Sequence of Enterococcus faecalis Strain CG_E

“…E. faecalis strain CG_E was isolated from biogas reactor content and initially designated E. faecalis CG01 (5). Maize silage and cattle as well as poultry dry manure were the main substrates supplied to the reactor, which is located in Troisdorf, Germany (6).…”

“…Maize silage and cattle as well as poultry dry manure were the main substrates supplied to the reactor, which is located in Troisdorf, Germany (6). …”