Organic acid production from starchy waste by gut derived microorganisms

There is a worldwide increasing energy demand while fossil resources are getting depleted. Using organic waste to produce valuable and renewable products such as organic acids including lactate and succinate is a promising strategy. In this study, starch waste was selected as the main substrate as it is abundant in many places and has low-value. Gut microorganisms from cow rumen fluids and guinea pig fecal samples were used as inocula to catalyze organic acid production. Microbial diversity involved in organic acid production was investigated. Succinate yields were as high as 4.52 mmol SA / gram Starch. Starch waste and rumen fluid are suitable for lactate and succinate production. In addition, three novel organic acid producing bacteria were obtained and some may have potential for future applications.</p

Organic acid production from potato starch waste fermentation by rumen microbial communities from Dutch and Thai dairy cows

Background: Exploring different microbial sources for biotechnological production of organic acids is important. Dutch and Thai cow rumen samples were used as inocula to produce organic acid from starch waste in anaerobic reactors. Organic acid production profiles were determined and microbial communities were compared using 16S ribosomal ribonucleic acid gene amplicon pyrosequencing. Results: In both reactors, lactate was the main initial product and was associated with growth of Streptococcus spp. (86% average relative abundance). Subsequently, lactate served as a substrate for secondary fermentations. In the reactor inoculated with rumen fluid from the Dutch cow, the relative abundance of Bacillus and Streptococcus increased from the start, and lactate, acetate, formate and ethanol were produced. From day 1.33 to 2, lactate and acetate were degraded, resulting in butyrate production. Butyrate production coincided with a decrease in relative abundance of Streptococcus spp. and increased relative abundances of bacteria of other groups, including Parabacteroides, Sporanaerobacter, Helicobacteraceae, Peptostreptococcaceae and Porphyromonadaceae. In the reactor with the Thai cow inoculum, Streptococcus spp. also increased from the start. When lactate was consumed, acetate, propionate and butyrate were produced (day 3-4). After day 3, bacteria belonging to five dominant groups, Bacteroides, Pse udoramibacter_Eubacterium, Dysgonomonas, Enterobacteriaceae and Porphyromonadaceae, were detected and these showed significant positive correlations with acetate, propionate and butyrate levels. Conclusions: The complexity of rumen microorganisms with high adaptation capacity makes rumen fluid a suitable source to convert organic waste into valuable products without the addition of hydrolytic enzymes. Starch waste is a source for organic acid production, especially lactate.Peer reviewe

Draft genome sequence of Actinomyces glycerinitolerans strain G10T, isolated from sheep rumen fluid

Actinomyces glycerinitolerans strain G10T, which was isolated from sheep rumen fluid, can metabolize a range of substrates, including complex carbohydrates to organic acids (OAs). Here, we report a 3.69-Mbp draft genome of Actinomyces glycerinitolerans

Draft genome sequence of Streptococcus caviae strain Cavy grass 6^T, isolated from domesticated guinea pig fecal samples

Streptococcus caviae strain Cavy grass 6T, isolated from fecal samples of pet guinea pigs, can metabolize a range of plant mono- and disaccharides, as well as polymeric carbohydrates. Here, we report the draft genome sequence of this strain, which comprises 2.11 Mb.</p

Draft genome sequence of Actinomyces succiniciruminis strain Am4^T, isolated from cow rumen fluid

Actinomyces succiniciruminis strain Am4T, isolated from cow rumen fluid, can metabolize a range of substrates including complex carbohydrates to organic acids. Here, we report a 3.33-Mbp draft genome of Actinomyces succiniciruminis.</p

Granular carbon-based electrodes as cathodes in methane-producing bioelectrochemical systems

Methane-producing bioelectrochemical systems generate methane by using microorganisms to reduce carbon dioxide at the cathode with external electricity supply. This technology provides an innovative approach for renewable electricity conversion and storage. Two key factors that need further attention are production of methane at high rate, and stable performance under intermittent electricity supply. To study these key factors, we have used two electrode materials: granular activated carbon (GAC) and graphite granules (GG). Under galvanostatic control, the biocathodes achieved methane production rates of around 65 L CH4/m2catproj/d at 35 A/m2catproj, which is 3.8 times higher than reported so far. We also operated all biocathodes with intermittent current supply (time-ON/time-OFF: 4–2′, 3–3′, 2–4′). Current-to-methane efficiencies of all biocathodes were stable around 60% at 10 A/m2catproj and slightly decreased with increasing OFF time at 35 A/m2catproj, but original performance of all biocathodes was recovered soon after intermittent operation. Interestingly, the GAC biocathodes had a lower overpotential than the GG biocathodes, with methane generation occurring at −0.52 V vs. Ag/AgCl for GAC and at −0.92 V for GG at a current density of 10 A/m2catproj. 16S rRNA gene analysis showed that Methanobacterium was the dominant methanogen and that the GAC biocathodes experienced a higher abundance of proteobacteria than the GG biocathodes. Both cathode materials show promise for the practical application of methane-producing BESs

Streptococcus caviae sp. nov., isolated from Guinea pig faecal samples

A novel cellobiose-degrading and lactate-producing bacterium, strain Cavy grass 6T, was isolated from faecal samples of guinea pigs (Cavia porcellus). Cells of the strain were ovalshaped, non-motile, non-spore-forming, Gram-stain-positive and facultatively anaerobic. The strain gr at 25–40 °C (optimum 37 °C) and pH 4.5–9.5 (optimum 8.0). Phylogenetic analysis based on 16S rRNA gene sequences showed that strain Cavy grass 6T belongs to the genus Streptococcus with its closest relative being Streptococcus devriesei CCUG 47155T with only 96.5% similarity. Comparing strain Cavy grass 6T and Streptococcus devriesei CCUG 47155T, average nucleotide identity and level of digital DNA–DNA hybridization dDDH were only 86.9 and 33.3%, respectively. Housekeeping genes groEL and gyrA were different between strain Cavy grass 6T and other streptococci. The G+C content of strain Cavy grass 6T was 42.6±0.3 mol%. The major (>10%) cellular fatty acids of strain Cavy grass 6T were C16:0, C20: 1ω9c and summed feature 8 (C18: 1ω7c and/or C18: 1ω6c). Strain Cavy grass 6T ferment a range of plant mono- and disaccharides as well as polymeric carbohydrates, including cellobiose, dulcitol, D-glucose, maltose, raffinose, sucrose, L-sorbose, trehalose, inulin and dried grass extract, to lactate, formate, acetate and ethanol. Based on phylogenetic and physiological characteristics, Cavy grass 6T can be distinguished from other members of the genus Streptococcus. Therefore, a novel species of the genus Streptococcus, family Streptococcaceae, order Lactobacillales is proposed, Streptococcus caviae sp. nov. (type strain Cavy grass 6T=TISTR 2371T=DSM 102819T).</p

Microbial Diversity and Organic Acid Production of Guinea Pig Faecal Samples

The guinea pig (Cavia porcellus) or cavy is a grass-eating rodent. Its main diet consists of grass or hay, which comprises cellulose, hemicellulose, lignin and their derivatives. Here, the microbial diversity of faecal samples of two guinea pigs and microbial enrichments made with substrates, including starch waste and dried grass, were investigated along with organic acid production profiles. The microbial communities of the faecal samples were dominated by the phyla Bacteroidetes (40%) and Firmicutes (36%). Bacteroidales S24-7 (11% in Cavy 1 and 21% in Cavy 2) was the most abundant order. At genus level, many microorganisms remained unclassified. Different carbon sources were used for organic acid production in faecal enrichments. The dominant bacterial groups in the secondary enrichments with dried grass, starch waste and xylose were closely related to Prevotella and Blautia. Acetate was the predominant organic acid from all enrichments. The organic acid production profiles corresponded to a mixed acid fermentation but differed depending on the substrate. Eight phylogenetically different isolates were obtained, including a novel Streptococcus species, strain Cavy grass 6. This strain had a low abundance (1%) in one of the faecal samples but was enriched in the dried grass enrichment (3%). Cavy grass 6, a fast-growing heterolactic bacterium, ferments cellobiose to lactate, acetate, formate and ethanol. Our results show that cavy faecal samples can be applied as microbial source for organic acid production from complex organic substrates. The cavy gut contains many as-yet-uncultivated bacteria which may be appropriate targets for future studies.</p

MOESM10 of Organic acid production from potato starch waste fermentation by rumen microbial communities from Dutch and Thai dairy cows

Additional file 10: Figure S3. Grouping tree of the bacterial communities from both reactors (a). PCA plot weighted unifraction of the relative abundance of the bacterial communities at different time points in the starch waste fermentation using the Dutch rumen fluid (red dots) and Thai rumen fluid (blue dots) (b)