Biosynthesis of pyruvic acid from glucose by Blastobotrys adeninivorans

Oxaloacetate stimulates phosphorylation of epidermal growth factor receptor in epithelial cells in vitro

Oxaloacetate (OA) is a pivotal endogenous metabolite. Within our investigation, we ascertained that OA functions as an agonist for the epidermal growth factor receptor (EGFR), a key protagonist in the genesis of diverse tumours. We substantiated that escalating concentrations of OA initially enhanced the cellular viability of several cancer cells, followed by subsequent attenuation, which is similar to the effect of EGF. Furthermore, the protein phosphorylation profile in HepG2 cells exposed to OA closely paralleled that induced by epidermal growth factor (EGF). Additional findings underscored the capability of OA to induce the generation of EGFR dimers. Finally, our observations revealed that OA governs the activation of AKT and Erk, the typical downstream signalling proteins of EGFR. We postulate that the endogenous metabolite OA can function as either an agonist or inhibitor of EGFR at specific concentrations to modulate tumour proliferation, and provide new insights into the regulation of EGFR activation.

Hepatic antioxidant capacity, immune response, and glycolysis of Tibetan sheep in response to dietary soluble protein levels

In recent years, the increasing cost of protein raw materials has significantly impacted feed expenses and presented challenges to the livestock industry. Ninety-two-month-old male Tibetan sheep (15.40±0.81 kg) were randomly divided into three groups based on protein levels in their diet: L group (12% protein), M group (14% protein), and H group (16% protein). The feeding experiment was performed for 100 days, including a 10-day adaption period. It was found that the liver cells of the M group exhibited a better uniform in cytoplasm. Additionally, group M sheep had higher levels of GSH-Px and T-AOC (P<0.05), as well as elevated IgM, IL-1β, IL-6, and SDH content compared to other groups (P<0.05). There were 577, 698, and 623 differentially expressed genes between groups H and L, groups H and M, and groups M and L, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that the DEGs regulated the activities of 56 pathways. Six liver-metabolism-related DEGs, SOD2, SOD1, CD19, IGF1, HK2, and PFKFB3, were expressed differently among the three sheep groups. In summary, a 14% protein level in the diet improved the hepatic antioxidant capacity, immune function, and glycolysis in Tibetan sheep through modulating the expression of functional genes.

Therapeutic effects and mechanisms of isoxanthohumol on DSS-induced colitis: regulating T cell development, restoring gut microbiota, and improving metabolic disorders

Ulcerative colitis (UC) is a severe hazard to human health. Since pathogenesis of UC is still unclear, current therapy for UC treatment is far from optimal. Isoxanthohumol (IXN), a prenylflavonoid from hops and beer, possesses anti-microbial, anti-oxidant, anti-inflammatory, and anti-angiogenic properties. However, the potential effects of IXN on the alleviation of colitis and the action of the mechanism is rarely studied. Here, we found that administration of IXN (60 mg/kg/day, gavage) significantly attenuated dextran sodium sulfate (DSS)-induced colitis, evidenced by reduced DAI scores and histological improvements, as well as suppressed the pro-inflammatory Th17/Th1 cells but promoted the anti-inflammatory Treg cells. Mechanically, oral IXN regulated T cell development, including inhibiting CD4+ T cell proliferation, promoting apoptosis, and regulating Treg/Th17 balance. Furthermore, IXN relieved colitis by restoring gut microbiota disorder and increasing gut microbiota diversity, which was manifested by maintaining the ratio of Firmicutes/Bacteroidetes balance, promoting abundance of Bacteroidetes and Ruminococcus, and suppressing abundance of proteobacteria. At the same time, the untargeted metabolic analysis of serum samples showed that IXN promoted the upregulation of D-( +)-mannose and L-threonine and regulated pyruvate metabolic pathway. Collectively, our findings revealed that IXN could be applied as a functional food component and served as a therapeutic agent for the treatment of UC.

The Production of Pyruvate in Biological Technology: A Critical Review

Pyruvic acid has numerous applications in the food, chemical, and pharmaceutical industries. The high costs of chemical synthesis have prevented the extensive use of pyruvate for many applications. Metabolic engineering and traditional strategies for mutation and selection have been applied to microorganisms to enhance their ability to produce pyruvate. In the past decades, different microbial strains were generated to enhance their pyruvate production capability. In addition to the development of genetic engineering and metabolic engineering in recent years, the metabolic transformation of wild-type yeast, E. coli, and so on to produce high-yielding pyruvate strains has become a hot spot. The strategy and the understanding of the central metabolism directly related to pyruvate production could provide valuable information for improvements in fermentation products. One of the goals of this review was to collect information regarding metabolically engineered strains and the microbial fermentation processes used to produce pyruvate in high yield and productivity.

Engineering of Yarrowia lipolytica for producing pyruvate from glycerol

The present study aims to increase pyruvate production by engineering Yarrowia lipolytica through modifying the glycerol metabolic pathway. Results: Wild-type Yarrowia lipolytica (Po1d) was engineered to produce six different strains, namely ZS099 (by over-expressing PYK1), ZS100 (by deleting DGA2), ZS101 (by over-expressing DAK1, DAK2, and GCY1), ZS102 (by over-expressing GUT1 and GUT2), ZS103 (by over-expressing GUT1) and ZSGP (by over-expressing POS5 and deleting GPD2). Production of pyruvate from engineered and control strains was determined using high-performance liquid chromatography (HPLC). Subsequently, the fermentation conditions for producing pyruvate were optimized, including the amount of initial inoculation, the addition of calcium carbonate (CaCO₃), thiamine and glycerol. Finally, for scaled-up purposes, a 20-L fermentor was used. It was observed that pyruvate production increased by 136% (8.55 g/L) in ZSGP strain compared to control (3.62 g/L). Furthermore, pyruvate production by ZSGP reached up to 110.4 g/L in 96 h in the scaled-up process. We conclude that ZSGP strain of Y. lipolytica can be effectively used for pyruvate production at the industrial level.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03158-7.

Beneficial Effects of Celastrol on Immune Balance by Modulating Gut Microbiota in Experimental Ulcerative Colitis Mice

Ulcerative colitis (UC) is a chronic inflammatory bowel disease caused by many factors including colonic inflammation and microbiota dysbiosis. Previous studies have indicated that celastrol (CSR) has strong anti-inflammatory and immune-inhibitory effects. Here, we investigated the effects of CSR on colonic inflammation and mucosal immunity in an experimental colitis model, and addressed the mechanism by which CSR exerts the protective effects. We characterized the therapeutic effects and the potential mechanism of CSR on treating UC using histological staining, intestinal permeability assay, cytokine assay, flow cytometry, fecal microbiota transplantation (FMT), 16S rRNA sequencing, untargeted metabolomics, and cell differentiation. CSR administration significantly ameliorated the dextran sodium sulfate (DSS)-induced colitis in mice, which was evidenced by the recovered body weight and colon length as well as the decreased disease activity index (DAI) score and intestinal permeability. Meanwhile, CSR down-regulated the production of pro-inflammatory cytokines and up-regulated the amount of anti-inflammatory mediators at both mRNA and protein levels, and improved the balances of Treg/Th1 and Treg/Th17 to maintain the colonic immune homeostasis. Notably, all the therapeutic effects were exerted in a gut microbiota-dependent manner. Furthermore, CSR treatment increased the gut microbiota diversity and changed the compositions of the gut microbiota and metabolites, which is probably associated with the gut microbiota-mediated protective effects. In conclusion, this study provides the strong evidence that CSR may be a promising therapeutic drug for UC.

Effects of carbon concentration, oxygen, and controlled pH on the engineering strain Lactiplantibacillus casei E1 in the production of bioethanol from sugarcane molasses

Sugarcane molasses are considered a potential source for bioethanol's commercial production because of its availability and low market price. It contains high concentrations of fermentable sugars that can be directly metabolized by microbial fermentation. Heterofermentative lactic acid bacteria, especially Lactiplantibacillus casei, have a high potential to be a biocatalyst in ethanol production that they are characterized by strong abilities of carbohydrate metabolism, ethanol synthesis, and high alcohol tolerance. This study aimed to evaluate the feasibility of producing ethanol by Lactiplantibacillus casei used the ethanologen engineering strain L. casei E1 as a starter culture and cane molasses as substrate medium. The effects of environmental factors on the metabolism of L. casei E1 were analyzed by high-performance liquid chromatography (HPLC) system, and the gene expression of key enzymes in carbon source metabolism was detected using quantitative real-time PCR (RT-qPCR). Results showed that the strain could grow well, ferment sugar quickly in cane molasses. By fermenting this bacterium anaerobically at 37 °C for 36 h incubation in 5 °BX molasses when the fermenter's pH was controlled at 6.0, ethanol yield reached 13.77 g/L, and carbohydrate utilization percentage was 78.60%. RT-qPCR results verified the strain preferentially ferment glucose and fructose of molasses to ethanol at the molecular level. In addition, the metabolism of sugars, especially fructose, would be inhibited by elevating acidity. Our findings support the theoretical basis for exploring Lactic acid bacteria as a starter culture for converting sugarcane molasses into ethanol.

Yeasts of the Blastobotrys genus are promising platform for lipid-based fuels and oleochemicals production

Strains of the yeast genus Blastobotrys (subphylum Saccharomycotina) represent a valuable biotechnological resource for basic biochemistry research, single-cell protein, and heterologous protein production processes. Species of this genus are dimorphic, non-pathogenic, thermotolerant, and can assimilate a variety of hydrophilic and hydrophobic substrates. These can constitute a single-cell oil platform in an emerging bio-based economy as oleaginous traits have been discovered recently. However, the regulatory network of lipogenesis in these yeasts is poorly understood. To keep pace with the growing market demands for lipid-derived products, it is critical to understand the lipid biosynthesis in these unconventional yeasts to pinpoint what governs the preferential channelling of carbon flux into lipids instead of the competing pathways. This review summarizes information relevant to the regulation of lipid metabolic pathways and prospects of metabolic engineering in Blastobotrys yeasts for their application in food, feed, and beyond, particularly for fatty acid-based fuels and oleochemicals. KEY POINTS: • The production of biolipids by heterotrophic yeasts is reviewed. • Summary of information concerning lipid metabolism regulation is highlighted. • Special focus on the importance of diacylglycerol acyltransferases encoding genes in improving lipid production is made.

Proteogenomics Study of Blastobotrys adeninivorans TMCC 70007-A Dominant Yeast in the Fermentation Process of Pu-erh Tea

Blastobotrys adeninivorans plays an essential role in pile-fermenting of Pu-erh tea. Its ability to assimilate various carbon and nitrogen sources makes it available for application in a wide range of industry sectors. The genome of B. adeninivorans TMCC 70007 isolated from pile-fermented Pu-erh tea was sequenced and assembled. Proteomics analysis indicated that 4900 proteins in TMCC 70007 were expressed under various culture conditions. Proteogenomics mapping revealed 48 previously unknown genes and corrected 118 gene models predicted by GeneMark-ES. Ortho-proteogenomics analysis identified 17 previously unidentified genes in B. adeninivorans LS3, the first strain with a sequenced genome among the genus Blastobotrys as well. More importantly, five species specific genes were identified from TMCC 70007, which could serve as a barcode for strain typing and were applicable for fermentation process protection of this industrial species. The datasets generated from tea aqueous extract culture not only increased the proteome coverage and accuracy but also contributed to the identification of proteins related to polyphenols and caffeine, which were considered to change greatly during the microbial fermentation of Pu-erh tea. This study provides a proteome perspective on TMCC 70007, which was considered to be an important strain in the production of Pu-erh tea. The systematic proteogenomics analysis not only made a better annotation on the genome of B. adeninivorans TMCC 70007 as previous proteogenomics study but also provided solution for fermentation process protection on valuable industrial species with species specific genes uniquely identified from proteogenomics study.

Pyruvate Production from Whey Powder by Metabolic Engineered Klebsiella oxytoca

Pyruvate is an important platform material widely used in food, pharmaceutical, and chemical industries. Pyruvate-tolerant Klebsiella oxytoca PDL-0 was chosen as a chassis for pyruvate production via metabolic engineering. Genes related to by-product generation were knocked out to decrease the production of 2,3-butantediol, acetate, ethanol, and succinate. The NADH oxidase encoding gene nox was inserted into the locus of the lactate dehydrogenase encoding gene ldhD in the genome of K. oxytoca to simultaneously block lactate production and regenerate NAD⁺. The pyruvate importers CstA and YjiY were identified, and their encoding genes were deleted to increase pyruvate accumulation. The engineered strain K. oxytoca PDL-YC produced 71.0 g/L pyruvate from glucose. Furthermore, K. oxytoca PDL-YC can use whey powder, an abundant by-product of the cheese making process, as substrate for pyruvate production. Pyruvate production with a concentration of 62.3 g/L and a productivity of 1.60 g/[L·h] was realized using whey powder as substrate.

Electrolyzing lactic acid in situ in fermentation broth to produce pyruvic acid in electrolysis cell

Pyruvic acid is an important chemical in the carboxylate platform. Obstacles for its implementation are the need for high energy in chemical synthesis and additives in fermentation leading to increased production costs. Here, pyruvic acid generation from direct conversion of lactic acid in fermentation broth by electrolysis method is presented. It was found that lactic acid could be converted to pyruvic acid in the electrolysis cell under alkaline conditions. Using 12.53 g/L lactic acid fermentation broth as anolyte, 7.01 g/L pyruvic acid could be produced and productivity to lactic acid was 57.66% at initial pH 11.74 and 5.0 V applied a voltage in the electrolysis cell. Meanwhile, 0.472 mol hydrogen was produced at the cathode. The electric energy efficiency was 76.18%. Lactic acid fermentation is relatively cheap and can be performed on many kinds of wastes and biomasses. The results suggest that pyruvic acid production from direct electrolysis of lactic acid fermentation broth can be economically feasible.

Biosynthesis of pyruvic acid from glycerol-containing substrates and its regulation in the yeast Yarrowia lipolytica

The ability of different yeasts to synthesize pyruvic acid (PA) from glycerol-containing substrates has been studied. The selected strain Yarrowia lipolytica VKM Y-2378 synthesized PA with α-ketoglutaric acid (KGA) as a byproduct. The content of KGA greatly depended on cultivation conditions. The minimal formation of the byproduct was provided by the limitation of yeast growth by thiamine (0.6 µg/g biomass); the use of ammonium sulfate (0.6%) as a nitrogen source; addition of glycerol to cultivation medium in 20 g/L portions; maintaining the cultivation temperature at 28 °C, pH of the cultivation medium at 4.5, and medium aeration between 55 and 60% of saturation; the optimal cultivation time was 48 h. The selected strain cultivated under such conditions in a fermenter with a waste glycerol from biodiesel production process synthesized 41 g/L PA with a yield of 0.82 g/g. The mechanism of PA production from glycerol-containing substrates in Y. lipolytica is discussed.

Separation and purification of α-ketoglutarate and pyruvate from the fermentation broth of Yarrowia lipolytica

A strategy to achieve the efficient co-production of α-ketoglutarate (KGA) and pyruvate (PYR) via Yarrowia lipolytica fermentation was established in our previous work. The next big challenge is to achieve an efficient separation of the two keto acids. A strategy for simultaneously separating and purifying KGA and PYR based on their different boiling points was established, leading to the efficient separation and purification of the two keto acids from the fermentation broth of Y. lipolytica. The purity and yield of KGA/PYR reached 99.3/99.5 and 79.8/80.6%, respectively. Application of the separation method on industrial scale could further decrease the cost of the production of the two keto acids by biotechnological routes.

Oxaloacetate induces apoptosis in HepG2 cells via inhibition of glycolysis

Most cancer cells perform glycolysis despite having sufficient oxygen. The specific metabolic pathways of cancer cells have become the focus of cancer treatment. Recently, accumulating evidence indicates oxidative phosphorylation (OXPHOS) and glycolysis can be regulated with each other. Thus, we suggest that the glycolysis of cancer cells is inhibited by restoring or improving OXPHOS in cancer cells. In our study, we found that oxaloacetate (OA) induced apoptosis in HepG2 cells in vivo and in vitro. Meanwhile, we found that OA induced a decrease in the energy metabolism of HepG2 cells. Further results showed that the expression and activity of glycolytic enzymes were decreased with OA treatment. Conversely, the expression and activity of enzymes involved in the TCA cycle and OXPHOS were increased with OA treatment. The results indicate that OA can inhibit glycolysis through enhancement of OXPHOS. In addition, OA‐mediated suppression of HIF1α, p‐Akt, and c‐myc led to a decrease in glycolysis level. Therefore, OA has the potential to be a novel anticancer drug.