Butyric Acid Production Research Articles

Fermentation quality of ratoon rice fermented with fermented juice of epiphytic lactic acid bacteria from tropicalgrass

This study aimed to determine the quality of fermented ratoon paddy silage as ruminant feed. The paddy material was obtained from rice fields in the Sukoharjo, Central Java, Indonesia. Turiang padi (Oryza sativa) at the cutting age of 14 days, with the Inpari 32 variety. The addition of an accelerator of Lactic Acid Bacteria or FJLB (fermented juice of epiphityc lactic acid bacteria) from Elephant Grass Extract (Pennisetum purpureum) and Odot Grass (Pennisetum purpureum CV. Mott) were incubated for 2 days. This research was conducted experimentally using a completely randomized design (CRD) with 5 replications for each treatment. The treatments consisted of no additives (T1), FJLB additives from elephant grass (T2) and odot grass (T3). FJLB was added as much as 1% of fresh weight. Silage fermentation was carried out for 21 days at room temperature. All data obtained were analyzed using the R Studio program. The Flieg point value showed the silage quality in the good and very good range. Butyric acid production is low and still within standard limits. The production of lactic acid was higher (P<0.05) in the silage of paddy ratoon which received additional silage additive from FJLB. It could be concluded that the addition of FJLB was able to improve the quality of the fermented ratoon rice.

Berberine activates PPARδ and promotes gut microbiota-derived butyric acid to suppress hepatocellular carcinoma

BackgroundPeroxisome proliferator-activated receptors (PPARs) are a family of ligand-inducible transcription factors that govern various essential metabolic activities in the liver and other organs. Recently, berberine (BBR) has been characterized as a modulator of PPARs; however, the matter of whether PPARs are involved in the inhibitory effect of BBR on hepatocellular carcinoma (HCC) is not well understood. PurposeThis study aimed to investigate the role of PPARs in the suppressive effect of BBR on HCC and to elucidate the relative mechanism. MethodsWe studied the role of PPARs in the anti-HCC effects of BBR both in vitro and in vivo. The mechanism whereby BBR regulated PPARs was studied using real-time PCR, immunoblotting, immunostaining, luciferase, and a chromatin immunoprecipitation coupled PCR assay. Additionally, we used adeno-associated virus (AAV)-mediated gene knockdown to address the effect of BBR more effectively. ResultsWe demonstrated that PPARδ played an active role in the anti-HCC effect of BBR, rather than PPARα or PPARγ. Following a PPARδ-dependent manner, BBR increased BAX, cleaved Caspase 3, and decreased BCL2 expression to trigger apoptotic death, thereby suppressing HCC development both in vitro and in vivo. It was noted that the interactions between PPARδ and the apoptotic pathway resulted from the BBR-induced upregulation of the PPARδ transcriptional function; that is, the BBR-induced activation of PPARδ could mediate the binding with the promoters of apoptotic genes such as Caspase 3, BAX, and BCL2. Moreover, gut microbiota also contributed to the suppressive effect of BBR on HCC. We found that BBR treatment restored the dysregulated gut microbiota induced by the liver tumor burden, and a functional gut microbial metabolite, butyric acid (BA), acted as a messenger in the gut microbiota-liver axis. Unlike BBR, the effects of BA suppressing HCC and activating PPARδ were not potent. However, BA was able to enhance the efficacy of BBR by reducing PPARδ degradation through a mechanism to inhibit the proteasome ubiquitin system. Additionally, we found that the anti-HCC effect of BBR or a combination of BBR and BA was much weaker in mice with AAV-mediated PPARδ knockdown than those in the control mice, suggesting the critical role of PPARδ. ConclusionIn summary, this study is the first to report that a liver-gut microbiota-PPARδ trilogy contributes to the anti-HCC effect of BBR. BBR not only directly activated PPARδ to trigger apoptotic death but also promoted gut microbiota-derived BA production, which could reduce PPARδ degradation to enhance the efficacy of BBR.

An optimized reverse β-oxidation pathway to produce selected medium-chain fatty acids in Saccharomyces cerevisiae

BackgroundMedium-chain fatty acids are molecules with applications in different industries and with growing demand. However, the current methods for their extraction are not environmentally sustainable. The reverse β-oxidation pathway is an energy-efficient pathway that produces medium-chain fatty acids in microorganisms, and its use in Saccharomyces cerevisiae, a broadly used industrial microorganism, is desired. However, the application of this pathway in this organism has so far either led to low titers or to the predominant production of short-chain fatty acids.ResultsWe genetically engineered Saccharomyces cerevisiae to produce the medium-chain fatty acids hexanoic and octanoic acid using novel variants of the reverse β-oxidation pathway. We first knocked out glycerolphosphate dehydrogenase GPD2 in an alcohol dehydrogenases knock-out strain (△adh1-5) to increase the NADH availability for the pathway, which significantly increased the production of butyric acid (78 mg/L) and hexanoic acid (2 mg/L) when the pathway was expressed from a plasmid with BktB as thiolase. Then, we tested different enzymes for the subsequent pathway reactions: the 3-hydroxyacyl-CoA dehydrogenase PaaH1 increased hexanoic acid production to 33 mg/L, and the expression of enoyl-CoA hydratases Crt2 or Ech was critical to producing octanoic acid, reaching titers of 40 mg/L in both cases. In all cases, Ter from Treponema denticola was the preferred trans-enoyl-CoA reductase. The titers of hexanoic acid and octanoic acid were further increased to almost 75 mg/L and 60 mg/L, respectively, when the pathway expression cassette was integrated into the genome and the fermentation was performed in a highly buffered YPD medium. We also co-expressed a butyryl-CoA pathway variant to increase the butyryl-CoA pool and support the chain extension. However, this mainly increased the titers of butyric acid and only slightly increased that of hexanoic acid. Finally, we also tested the deletion of two potential medium-chain acyl-CoA depleting reactions catalyzed by the thioesterase Tes1 and the medium-chain fatty acyl CoA synthase Faa2. However, their deletion did not affect the production titers.ConclusionsBy engineering the NADH metabolism and testing different reverse β-oxidation pathway variants, we extended the product spectrum and obtained the highest titers of octanoic acid and hexanoic acid reported in S. cerevisiae. Product toxicity and enzyme specificity must be addressed for the industrial application of the pathway in this organism.

Metagenomic Sequencing Reveals the Taxonomic and Functional Characteristics of Rumen Micro-organisms in Gayals.

As a semi-wild breed, Gayals have a strong fiber degradation capacity, which is unique to the microbial structure and function of their rumen. In this study, the unique rumen microbial composition and function of Gayals were investigated by metagenomic sequencing, with the Yunnan yellow cattle as the control. We compared the differences in rumen micro-organisms between Gayals and the Yunnan Yellow cattle, and the results showed that there were differences in bacteria, archaea and fungi between Gayals and the Yunnan Yellow cattle, while no significant abundance changes were observed in the protozoa. In addition, the ratio of Firmicutes to Bacteroidetes (1.06) in Gayals was higher than that of the Yunnan Yellow cattle (0.66). Three enzymes (PTA, ACH and FTHFS) related to the acetate production pathway and five enzymes (BHBD, THL, PTB, BK and BCACT) involved in butyric acid production were annotated in this study. The CAZymes search results showed that the abundance of GH5, GH26, GH94, CBM11 and CBM63 in Gayals was higher than in the Yunnan Yellow cattle (p < 0.05). Furthermore, this research constructed a model of rumen micro-organisms degrading fibers according to the characteristics and differences in the rumen microbiota structures and functions of the two breeds. This study expands our knowledge of the rumen microbiota and the mechanisms of fiber degradation in Gayals.

Effects of Steaming on Sweet Potato Soluble Dietary Fiber: Content, Structure, and Lactobacillus Proliferation In Vitro.

The influence of steaming treatment on the soluble dietary fiber (SDF) of sweet potato was investigated. The SDF content increased from 2.21 to 4.04 g/100 g (in dry basis) during 20 min of steaming. The microcosmic morphology of the fractured cell wall indicated the release of SDF components during steaming. The SDF from fresh (SDF-F) and 20 min steamed (SDF-S) sweet potato was characterized. The neutral carbohydrates and uronic acid levels in SDF-S were significantly higher than SDF-F (59.31% versus 46.83%, and 25.36% versus 9.60%, respectively) (p < 0.05). The molecular weight of SDF-S was smaller than SDF-F (5.32 kDa versus 28.79 kDa). The probiotic property was evaluated by four Lactobacillus spp. fermentation in vitro with these SDF as carbon source, using inulin as the references. SDF-F showed the best proliferation effects on the four Lactobacillus spp. in terms of the OD600 and pH in cultures, and the highest production of propanoic acid and butyric acid after 24 h fermentation. SDF-S presented higher Lactobacillus proliferation effects, but slight lower propanoic acid and butyric acid production than inulin. It was concluded that 20 min of steaming released SDF with inferior probiotic properties, which might derive from the degraded pectin, cell wall components, and resistant dextrin.

The specificity of ten non-digestible carbohydrates to enhance butyrate-producing bacteria and butyrate production in vitro fermentation

Butyrate and butyrate-producing bacteria are important indicators of gut microbial metabolism in human health. Ten non-digestible carbohydrates (NDCs), including inulin, fructooligosaccharide (FOS), oats β-glucans (OGS), oats β-glucan oligosaccharides (OGOS), Astragalus polysaccharides (APS), Astragalus oligosaccharides (AOS), xanthan gum oligosaccharides (XGOS), gellan gum oligosaccharides (GGOS), curdlan oligosaccharides (COS), and pullulan oligosaccharides (POS) were used to investigate NDC specificity in modulating butyrate-producing bacteria and butyrate production in 48-h in vitro fermentation studies in combination with fecal inocula from 7 healthy donors and 11 patients with type 2 diabetes (T2D). We observed that the amount of these ten NDCs utilized depended on NDC structure and inter-individual gut microbial differences. XGOS and GGOS fermentations significantly increased butyrate-producing bacteria (especially f_Lachnospiraceae) and butyric acid production. Furthermore, XGOS and GGOS fermentations showed a better ability to consistently modulate gut microbiota composition and metabolic properties between individuals of healthy donors or T2D patients when compared to inulin, FOS, APS, AOS, OGS, OGOS, COS and POS fermentation. This research indicated that xanthan gum and gellan gum oligosaccharides have strong specificity to enhance butyrate-producing bacteria and butyrate production.

Boosting butyrate and hydrogen production in acidogenic fermentation of food waste and sewage sludge mixture: a pilot scale demonstration

Within the urban scenario, the application of a biorefinery technology value chain can foster the conversion of different organic substrates into marketable and added-value products. In this work, a pilot-scale dark fermentation (DF) process has been carried out as a key step for volatile fatty acids (VFA) and hydrogen production from the liquid fraction of sewage sludge and food waste mixture. Six operating conditions have been monitored in terms of yield and process stability, by changing the hydraulic retention time (HRT) from 4 to 6 days and applying a short-term hyper-thermophilic hydrolysis (70 °C, 8 h) on the same feedstock mixture. A tubular centrifugation was utilized to remove part of the biosolids (driven to biogas production) before the DF step, which was applied on the soluble and/or colloidal organic matter only. The hydrolysis step favored the following acidification process, in which a fermentation yield up to 0.42 g CODVFA/g VS0 was achieved at 5 days as HRT. Hydrogen production (up to 34.4% v/v and 0.046 m3 H2/kg VS0) was positively affected by the hydrolysis application and by the decrease of the HRT, highlighting the possibility to produce biohythane in the modeled two-phases anaerobic bioprocess. On the other hand, without the application of the hydrolysis, a selective production of butyric acid (up to 75% COD basin) was achieved, furnishing a different valorization route for the chosen urban organic feedstock. Changes in operating conditions and performances were also reflected by the adaptation of the microbial community, whose characterization highlighted the occurrence of several fermentative microorganisms (e.g., Clostridiaceae, Ruminococcaceae).

Sustainable production of drop-in butyric acid from bioderived poly(3-hydroxybutyrate)

A novel hydrogenolysis pathway is developed for producing butyric acid (BA) from bioderived poly(3-hydroxybutyrate) (PHB). The sustainable process exhibited obvious merits, including (1) one-pot reaction at mild temperature (e.g., 200 °C), (2) solvent- and catalyst-free system, (3) high yield (94 wt%) and purity (96%) of drop-in BA obtained. This work paves the way for sustainable production of BA with low-energy consumption and simple post-treatment.

Butyric acid: fermentation production using organic waste as low-cost feedstocks

Abstract Butyric acid is an important chemical which has many applications in the chemical, food, and pharmaceutical industries. Butyraldehyde, which is derived from propylene, is now converted into butyrate by petrochemical processes known as oxo synthesis. Because of its poor productivity and low butyrate concentration in the fermentation broth, biotechnological production of butyric acid is not economically viable. Typically, a sizable amount of the overall production expenses goes toward the cost of the fermentation substrate. If the fermentation process can use minimal biomass as the feedstock, a cost-competitive production of butyric acid from the fermentation technique would be generated with a strong market prospect. Organic wastes are recommended as a source of butyric acid fermentation feedstock because they are inexpensive, can be generated in huge numbers, and are biodegradable. With a focus on the low-cost feedstock, the many uses of butyric acid are discussed, with its present production status. As a result, this paper explores several butyric acid fermentation-related problems and offers ideas for potential solutions.

Chimonanthus salicifolius extract alleviates DSS-induced colitis and regulates gut microbiota in mice.

Ulcerative colitis is a chronic and recurrent gastrointestinal intestinal disease accompanied by inflammatory disorders, immunologic inadequacy, and intestinal flora dysbiosis, and current therapeutic pharmaceuticals have limited side effects. In this study, we revealed the extraction method of Chimonanthus salicifolius, analyzed the main component, compared the effect of its extract, Lactobacillus, and conventional drugs with different properties on DSS (dextran sodium sulfate)-induced colitis, and indicated extract regulatory properties of inestinal flora. A colitis model was established on experimental design, and BALB/c mice (male, 7 weeks old) were randomly assigned to five groups (n=10): control, DSS model, Chimonanthus salicifolius extract (CSE), Lactobacillus rhamnosus GG (LGG), and 5-aminosalicylic acid (5-ASA) groups. The three treatments could alleviate the symptoms and remit inflammation induced by DSS, in which CSE and LGG groups could both decrease the proinflammatory cytokine IL-6, IL-8, and TNF-α levels and increase anti-inflammatory cytokines IL-10 and TGF-β. The CSE intervention significantly promoted the higher production of butyric acid than LGG and 5-ASA groups (p < .05) after DSS challenge. Analysis of intestinal flora showed that CSE administration remarkably decreased the relative abundance of pathogenic bacteria Heliobacteriaceae and Peptococcaceae and exhibited higher abundance of Lactobacillaceae and Bifidobacterium than LGG in intestinal tract of mice (p < .05). These findings indicated that Chimonanthus salicifolius extract may have been beneficial for preventing and treating colitis.

Stress Hormone Adrenaline Boosts the Antibacterial Properties of L. plantarum and E. hallii

Amid intense exercise, the human body’s quick adaptability to stressful conditions is vital to cellular function, initiating what we recognize as an “adrenaline rush”. Despite findings on the in vitro interaction of adrenaline with the gut microbiome to regulate its virulence gene expression through AI-3 quorum sensing, studies conducted to examine the influence of the stress hormone adrenaline released through exercise on the function of the microbiome in our gut are yet insufficient. The human gut consists of a variety of microbes such as L. plantarum and E. hallii that hold vital roles in maintaining metabolic balance in the gut microbiome. Through our research, we envisioned investigating how adrenaline treatment at different time intervals or concentrations mirroring the various circumstances of exercise may affect bacterial growth, antibacterial substance production, and their antibacterial properties. While both bacteria were not affected in its growth for 48 hours, in L. plantarum, demonstrating decreased growth in the first 8 hours, its main functions — lactic acid production — were furthered with the hormone. In E. hallii, butyric acid production, with the hormone, significantly increased in its supernatant, and the intermediate treatment of adrenaline for 8 hours served to catalyze the rate at which the bacteria reached its stationary phase of growth. The study holds great promise for future investigations on how such a mechanism can be applied to therapies boosting our existing abilities of protein disposal directly correlated to the prevention of diseases. What remains is, nevertheless, the discussion regarding the true control center of these bacteria that interact with adrenaline to cause changes in the antibiotic properties, function, and growth. In other words, future studies can be oriented towards understanding the changes in the antibacterial properties of given bacteria not indirectly through chemicals with antibacterial traits but rather through the quantitative measurement of growth inhibition with other bacteria or organisms.

Process Design for the Sustainable Production of Butyric Acid Using Techno-Economic Analysis and Life Cycle Assessment

Process Design for the Sustainable Production of Butyric Acid Using Techno-Economic Analysis and Life Cycle Assessment

Soluble, Diferuloylated Corn Bran Glucuronoarabinoxylans Modulate the Human Gut Microbiota In Vitro.

Corn bran is exceptionally rich in substituted glucuronoarabinoxylan polysaccharides, which are monoferuloylated and cross-linked by diferulic acid moieties. Here, we assessed the potential prebiotic activity of three enzymatically solubilized corn bran glucuronoarabinoxylans: medium feruloylated (FGAX-M), laccase cross-linked FGAX-M (FGAX-H), and alkali-treated FGAX-M devoid of feruloyl substitutions (FGAX-B). We examined the influence of these soluble FGAX samples on the gut microbiome composition and functionality during in vitro simulated colon fermentations, determined by 16S rRNA gene amplicon sequencing and assessment of short-chain fatty acid (SCFAs) production. All FGAX samples induced changes in the relative composition of the microbiota and the SCFA levels after 24 h of in vitro fermentation. The changes induced by FGAX-M and FGAX-H tended to be more profound and more similar to the changes induced by inulin than changes conferred by FGAX-B. The microbiota changes induced by FGAX-M and FGAX-H correlated with an increase in the relative abundance of Anaerostipes and with increased butyric acid production, while the changes induced by the FGAX-B sample were less compelling. The results imply that solubilized, substituted diferuloylated corn bran glucuronoarabinoxylans may be potential prebiotic candidates and that both single feruloylations and diferuloyl cross-links influence the prebiotic potential of these arabinoxylan compounds.

Construction of Clostridium tyrobutyricum strain and ionic membrane technology combination pattern for refinery final molasses recovery and butyric acid production.

Clostridium tyrobutyricum has considerable prospect in the production of organic acids. Globally, refinery final molasses is rich in sugar and reported to have high levels of accumulation and high emission costs, recognized as an excellent substrate for C. tyrobutyricum fermentation, but there is no suitable method available at present. In this study, an acid-base treatment combined with a new green membrane treatment technology - a dynamic ion-exchange membrane -was used to pretreat refinery final molasses, so that it could be used for C. tyrobutyricum to produce butyric acid. A high-performance liquid chromatography method was established to determine the conversion of a large amount of sucrose into fermentable sugars (71.88 g/L glucose and 38.06 g/L fructose) in the treated refinery final molasses. The process of sequential filtration with 3, 1, and 0.45 μm-pore diameter dynamic ion-exchange membranes could remove impurities, pigments, and harmful substances from the refinery final molasses, and retain the fermentable sugar. This means that refinery final molasses from the sugar industry could be utilized as a high-value by-product and used for the growth of C. tyrobutyricum, with industrial feasibility and economic competitiveness. Using the treated refinery final molasses as a carbon source, C. tyrobutyricum was screened by the method of adaptive evolution. The strain with butyric acid yielded 52.54 g/L, and the yield of the six carbon sugar was increased from 0.240 to 0.478 g/g. The results showed that combination of C. tyrobutyricum and ionic membrane technology broke through the bottleneck of its utilization of refinery final molasses. This study provided an innovative idea for the C. tyrobutyricum fermentation to produce butyric acid.

Pu-erh tea alleviated colitis-mediated brain dysfunction by promoting butyric acid production.

Brain inflammation develops with increased colitis. Pu-erh tea is considered a potential dietary intervention to improve colitis. However, it's unclear whether Pu-erh tea helps alleviate colitis-mediated brain dysfunction. Here, we found that colitis triggered brain dysfunction and increased the risk of depression. Pu-erh tea improved gut-brain barrier function (increased ZO-1 and Occludin) and restored short-chain fatty acids (SCFAs) as well as neurotransmitter release (γ-GABA, 5-HT, and dopamine), which stemmed from the production of butyric acid (BA). Pu-erh tea and BA promoted the production of SCFAs by reshaping the gut microbes (increased Lactobacillus, Akkermansia, Faecalibaculum), thereby downregulating gut inflammatory protein expression (PI3K/AKT/NF-κB). SCFAs, especially BA, intervened directly in the blood-brain barrier via the gut-brain axis to restore neurotransmitter release. Collectively, our results highlighted that increasing BA through Pu-erh tea consumption may be a key mechanism for improving colitis-mediated brain dysfunction by lowering gut inflammation and balancing gut microbe-gut-brain axis homeostasis. These results provide a promising step that might encourage further investigations of Pu-erh tea as a protective agent for brain function in colitis patients.

Porphyra haitanensis Polysaccharides Attenuates Blood Lipid via Gut-Liver Axis in Diet-Induced High-Fat Mesocricetus auratus through Multiple Integrated Omics.

Hyperlipidemia is currently a global public health problem severely affecting people's physical and mental health, as well as their quality of life. The present study is aimed at revealing the mechanism of Porphyra haitanensis polysaccharide (PHP) in decreasing blood lipids by acting through gut-liver axis in Mesocricetus auratus fed a high-fat diet. PHP significantly prevented increases in serum total cholesterol, triglycerides and low-density lipoprotein cholesterol, and alleviated damage to liver cells induced by a high-fat diet M. auratus, in a dose-dependent manner. PHP promotes proliferation of Muribaculaceae and Faecalibaculum, thereby enhancing the production of butyric acid both in the colon and liver, particularly high-dose PHP (HPHP). Low-dose PHP (LPHP) promotes the expression of phosphatidylcholine metabolites and fatty acid transport genes, and inhibits the expression of genes involved in fat degradation (Abhd5), adipogenesis (Me1), fatty acid synthesis (Fasn and Pnpla3), and fatty acid chain elongation (Elovl6) in the liver. However, HPHP inhibits the expression of triglyceride metabolites and promotes the expression of fatty acid transporter (CD36), fatty acid oxidation (Acacb), and peroxisome proliferator-activated receptor gamma (PPARg)genes in the liver. PHP regulates lipid metabolism through the gut microbiota, and the gut-liver axis plays an important role in its hypolipidemic effects.

Structural changes of butyrylated lotus seed starch and its impact on the gut microbiota of rat in vitro fermentation

Starch acylated with short-chain fatty acids (SCFAs), as type 4 resistant starch, can transport specific SCFAs to the colon and promote intestinal health. The objective was to investigate the effect of butyrylated lotus seed starches (LSBs) with different degrees of substitution (DS) on gut microbiota and butyrate production in vitro fermentation and to construct the relationship with its structural changes. The results of substrate structure change showed that the amorphous region of LSBs hydrolyzed firstly, the content of the subcrystalline region increased, and the molecular weight decreased. LSBs with higher DS had better fermentation characteristics, and more butyric acid production. A certain abundance of beneficial gut microbiota was significantly promoted. The Lotus seed resistant starch (LRS) group produced butyrate mainly by promoting the proliferation of Romboutsia. LSBs with low and medium DS mainly produced butyric acid by promoting Clostridium. LSBs with high DS produced butyric acid by promoting Lactobacillus, and Ruminococcaceae, by inhibiting Enterococcus, and Bacteroides. The study clarified the mechanism of butyric acid production was LSB's targeting the gut microbiota, which provided a scientific basis for the development of new prebiotics with high butyric acid production.

Production of butyric acid by different strains of Lactobacillus plantarum (Lactiplantibacillus plantarum)

The butyric acid content produced by three Lactobacillus plantarum (Lactiplantibacillus plantarum) strains (FP37, FP38 and FP48) deposited as probiotic strains was determined. The experimentation was carried out to evaluate whether the production of butyric acid was due to lipolytic activity for the presence of specific lipases or was related to the fermentation of saccharides. Therefore, the three strains were inoculated in different substrates with and without the addition of fat (tributyrin). The free butyric acid contents were determined by gas chromatography after distilling each culture medium. The results showed that butyric acid production occurred mainly in the substrates supplemented with fat and therefore it was linked to the activity of specific L. plantarum lipase. The L. plantarum FP48 strain produced the highest amount of butyric acid in fat substrates and could be a useful strain in the development of dairy products with functional properties.

Increasing lysine level improved methanol assimilation toward butyric acid production in Butyribacterium methylotrophicum

BackgroundMethanol, a promising non-food fermentation substrate, has gained increasing interest as an alternative feedstock to sugars for the bio-based production of value-added chemicals. Butyribacterium methylotrophicum, one of methylotrophic-acetogenic bacterium, is a promising host to assimilate methanol coupled with CO2 fixation for the production of organic acids, such as butyric acid. Although the methanol utilization pathway has been identified in B. methylotrophicum, little knowledge was currently known about its regulatory targets, limiting the rational engineering to improve methanol utilization.ResultsIn this study, we found that methanol assimilation of B. methylotrophicum could be significantly improved when using corn steep liquor (CSL) as the co-substrate. The further investigation revealed that high level of lysine was responsible for enhanced methanol utilization. Through the transcriptome analysis, we proposed a potential mechanism by which lysine confers improved methylotrophy via modulating NikABCDE and FhuBCD transporters, both of which are involved in the uptake of cofactors essential for enzymes of methanol assimilation. The improved methylotrophy was also confirmed by overexpressing NikABCDE or FhuBCD operon. Finally, the de novo synthetic pathway of lysine was further engineered and the methanol utilization and butyric acid production of B. methylotrophicum were improved by 63.2% and 79.7%, respectively. After an optimization of cultivation medium, 3.69 g/L of butyric acid was finally achieved from methanol with a yield of 76.3%, the highest level reported to date.ConclusionThis study revealed a novel mechanism to regulate methanol assimilation by lysine in B. methylotrophicum and engineered it to improve methanol bioconversion to butyric acid, culminating in the synthesis of the highest butyric acid titer reported so far in B. methylotrophicum. What’s more, our work represents a further advancement in the engineering of methylotrophic-acetogenic bacterium to improve C1-compound utilization.Graphical

Fermentation Supernatant of Elderly Feces with Inulin and Partially Hydrolyzed Guar Gum Maintains the Barrier of Inflammation-Induced Caco-2/HT29-MTX-E12 Co-Cultured Cells.

Intestinal barrier function declines with aging. We evaluated the effect of dietary fibers and indigestible oligosaccharides on intestinal barrier function by altering the microbiota of the elderly. The feces were anaerobically cultured with indigestible dextrin, inulin, partially hydrolyzed guar gum (PHGG), lactulose, raffinose, or alginate, and the fermented supernatant was added to inflammation-induced Caco-2/HT29-MTX-E12 co-cultured cells. Our data showed that inulin- and PHGG-derived supernatants exerted a protective effect on the intestinal barrier. The protective effect was significantly positively correlated with total short-chain fatty acids (SCFAs) and butyric acid production in the supernatant and negatively correlated with the claudin-2 (CLDN2) gene expression in the cultured cells. Furthermore, we showed that the CLDN2 levels are regulated by butyric acid. Thus, inulin and PHGG can change the intestinal environment of the elderly and maintain the intestinal barrier by accelerating the production of SCFAs and modifying the expression levels of barrier function-related genes.