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Shifting the balance of fermentation products between hydrogen and volatile fatty acids: microbial community structure and function.

ABSTRACT: Fermentation is a key process in many anaerobic environments. Varying the concentration of electron donor fed to a fermenting community is known to shift the distribution of products between hydrogen, fatty acids and alcohols. Work to date has focused mainly on the fermentation of glucose, and how the microbial community structure is affected has not been explored. We fed ethanol, lactate, glucose, sucrose or molasses at 100 me- eq. L-1, 200 me- eq. L-1 or 400 me- eq. L-1 to batch-fed cultures with fermenting, methanogenic communities. In communities fed high concentrations of electron donor, the fraction of electrons channeled to methane decreased, from 34% to 6%, while the fraction of electrons channeled to short chain fatty acids increased, from 52% to 82%, averaged across all electron donors. Ethanol-fed cultures did not produce propionate, but did show an increase in electrons directed to acetate as initial ethanol concentration increased. In glucose, sucrose, molasses and lactate-fed cultures, propionate accumulation co-occurred with known propionate producing organisms. Overall, microbial communities were determined by the substrate provided, rather than its initial concentration, indicating that a change in community function, rather than community structure, is responsible for shifts in the fermentation products produced.

SUBMITTER: Miceli JF

PROVIDER: S-EPMC5975917 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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Shifting the balance of fermentation products between hydrogen and volatile fatty acids: microbial community structure and function.

Miceli Joseph F JF Torres César I CI Krajmalnik-Brown Rosa R

FEMS microbiology ecology 20160914 12

Fermentation is a key process in many anaerobic environments. Varying the concentration of electron donor fed to a fermenting community is known to shift the distribution of products between hydrogen, fatty acids and alcohols. Work to date has focused mainly on the fermentation of glucose, and how the microbial community structure is affected has not been explored. We fed ethanol, lactate, glucose, sucrose or molasses at 100 me- eq. L<sup>-1</sup>, 200 me- eq. L<sup>-1</sup> or 400 me- eq. L<sup ...[more]

PMID: 27633926

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Project description:BackgroundThe co-fermentation of syngas (mainly CO, H2 and CO2) and different concentrations of carbohydrate/protein synthetic wastewater to produce volatile fatty acids (VFAs) was conducted in the present study.ResultsIt was found that co-fermentation of syngas with carbohydrate-rich synthetic wastewater could enhance the conversion efficiency of syngas and the most efficient conversion of syngas was obtained by co-fermentation of syngas with 5 g/L glucose, which resulted in 25% and 43% increased conversion efficiencies of CO and H2, compared to syngas alone. The protein-rich synthetic wastewater as co-substrate, however, had inhibition on syngas conversion due to the presence of high concentration of NH4 +-N (> 900 mg/L) produced from protein degradation. qPCR analysis found higher concentration of acetogens, which could use CO and H2, was present in syngas and glucose co-fermentation system, compared to glucose solo-fermentation or syngas solo-fermentation. In addition, the known acetogen Clostridium formicoaceticum, which could utilize both carbohydrate and CO/H2 was enriched in syngas solo-fermentation and syngas with glucose co-fermentation. In addition, butyrate was detected in syngas and glucose co-fermentation system, compared to glucose solo-fermentation. The detected n-butyrate could be converted from acetate and lactate/ethanol which produced from glucose in syngas and glucose co-fermentation system supported by label-free quantitative proteomic analysis.ConclusionsThese results demonstrated that the co-fermentation with syngas and carbohydrate-rich wastewater could be a promising technology to increase the conversion of syngas to VFAs. In addition, the syngas and glucose co-fermentation system could change the degradation pathway of glucose in co-fermentation and produce fatty acids with longer carbon chain supported by microbial community and label-free quantitative proteomic analysis. The above results are innovative and lead to achieve effective conversion of syngas into VFAs/longer chain fatty acids, which would for sure have a great interest for the scientific and engineering community. Furthermore, the present study also used the combination of high-throughput sequencing of 16S rRNA genes, qPCR analysis and label-free quantitative proteomic analysis to provide deep insights of the co-fermentation process from the taxonomic and proteomic aspects, which should be applied for future studies relating with anaerobic fermentation.

Project description:Simple Summary Acheta domesticus (house cricket) flour is one of the most promising and sustainable sources of nutrients. It is rich in protein, minerals, fatty acids, amino acids, and vitamins and it has a low impact on the consumption of natural environmental resources. On the other side, fermentation with lactic acid bacteria represents a technological tool that can improve further the nutritional quality of flours. Therefore, the aim of the present research was to study the adaptability of the Lactobacillus plantarum strain on insect flour fermentation. Fatty acids, amino acids, minerals, and aroma volatile compounds were analyzed during 48 h of fermentation. Fermentation improved the nutritional quantity of the bioactive compounds, mainly after 24 h of fermentation, where they reached higher extended values. Overall, our findings indicate that insect flour is able to support the growth and development of the Lactobacillus plantarum strain, leading to an enriched insect flour sourdough that could be further used in the manufacturing of new products. Abstract Acheta domesticus (L.1758) has been recently accepted by the European Union as a novel food, being the third insect that has been approved for human consumption. Nowadays, researchers’ attention is focused on exploiting new protein sustainable sources, and, therefore, insect flour has gained more and more interest. Organic acids, fatty acids, amino acids, aroma volatile compounds, and minerals were analyzed through HPLC-RID (High-performance liquid chromatography), GC-MS (Gas chromatography-mass spectrometry), LC-MS (Liquid chromatography–mass spectrometry), ITEX/GC-MS and AAS (Atomic Absorption Spectrophotometry), respectively. Fermentation of the insect flour with Lactobacillus plantarum ATCC 8014 strain (Lp) leads to an increase in organic acids such as lactic, acetic, and oxalic, whilst citric acid decreases its value. SFA (saturated fatty acids) and MUFA (monosaturated fatty acids) groups were positively influenced by Lp fermentation; meanwhile, PUFA (polysaturated fatty acids) decreased during fermentation. A positive trend was observed for amino acids, aroma volatile content, and minerals enhancement during insect sourdough fermentation, mainly at 24 h of fermentation. Acheta domesticus (A. domesticus) sourdough fermentation represents a new tool that needs to be further exploited aiming to improve the nutritional qualities of the final products.

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Shifting the balance of fermentation products between hydrogen and volatile fatty acids: microbial community structure and function.

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Shifting the balance of fermentation products between hydrogen and volatile fatty acids: microbial community structure and function.

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