Engineering of the metabolism of Saccharomyces cerevisiae for anaerobic production of mannitol

Metarhizium anisopliae JEF-197 Loses Glucose Metabolism in Surviving Japanese Pine Sawyer Beetle Against the Fungal Pathogen

Japanese pine sawyer beetle (JPSB), Monochamus alternatus is a forest insect pest with damaging to pine trees through vectoring plant-parasitic nematodes. In our previous work, the entomopathogenic Metarhizium anisopliae JEF-197 was effective in controlling JPSB adults. However some of JPSB adults survived well even against the fungal treatment. Now here in this work, we analyzed the transcriptome of JEF-197 from the fungus-treated JPSB adults which still survived in 8 days after the treatment. The day was determined based on the lethal time 50 (LT50) in our previous study. As a control, JEF-197 was cultured on 1/4SDA for 8 days. The plate-cultured JEF-197 transcripts were used for building-up an index in the abundance analysis using kallisto to investigate the gene regulation. Additionally, transcripts from the JEF-197-treated PSB were analyzed to find possible fungal transcripts to enlarge the index of abundance analysis. In the following differentially expressed gene (DEG) analysis, most JEF-197 transcripts showed significant down-regulations in JPSB adults 8 days after treatment, which were presented as clustering heatmap, PCA, MA and Volcano plots. The GO enrichment analysis showed similar results, in which most of pathways were significantly suppressed. Metabolic and biosynthesis metabolisms were most dominantly downregulated pathways. Particularly, many genes of glucose metabolisms were significantly suppressed, including genes for glycolysis, TCA, ATP & nucleotide synthesis, and glycogen & chitin production. This work suggests that JEF-197 lost its own glucose metabolism in the survived JPSB adults, and the survival could be involved in the active and continuous host defense mechanisms. It gives us questions what factors would be involved in the different response of individual to the fungal treatment and what happens if live and dead hosts were pooled in RNA-sequencing.

Metabolic engineering of Corynebacterium crenatum for enhanced L-tyrosine production from mannitol and glucose

BACKGROUND

L-Tyrosine (L-Tyr) is a significant aromatic amino acid that is experiencing an increasing demand in the market due to its distinctive characteristics. Traditional production methods exhibit various limitations, prompting researchers to place greater emphasis on microbial synthesis as an alternative approach.

RESULTS

Here, we developed a metabolic engineering-based method for efficient production of L-Tyr from Corynebacterium crenatum, including the elimination of competing pathways, the overexpression of aroB, aroD, and aroE, and the introduction of the mutated E. coli tyrAfbr gene for elevating L-Tyr generation. Moreover, the mtlR gene was knocked out, and the mtlD and pfkB genes were overexpressed, allowing C. crenatum to produce L-Tyr from mannitol. The L-Tyr production achieved 6.42 g/L at a glucose-to-mannitol ratio of 3:1 in a shake flask, which was 16.9% higher than that of glucose alone. Notably, the L-Tyr production of the fed-batch fermentation was elevated to 34.6 g/L, exhibiting the highest titers among those of C. glutamicum previously reported.

CONCLUSION

The importance of this research is underscored by its pioneering application of mannitol as a carbon source for the biosynthesis of L-Tyr, as well as its examination of the influence of mannitol-associated genes in microbial metabolism. A promising platform is provided for the production of target compounds that does not compete with human food source.

Utilizing yeasts for the conversion of renewable feedstocks to sugar alcohols - a review

Sugar alcohols are widely marketed compounds. They are useful building block chemicals and of particular value as low- or non-calorigenic sweeteners, serving as sugar substitutes in the food industry. To date most sugar alcohols are produced by chemical routes using pure sugars, but a transition towards the use of renewable, non-edible feedstocks is anticipated. Several yeasts are naturally able to convert renewable feedstocks, such as lignocellulosic substrates, glycerol and molasses, into sugar alcohols. These bioconversions often face difficulties to obtain sufficiently high yields and productivities necessary for industrialization. This review provides insight into the most recent studies on utilizing yeasts for the conversion of renewable feedstocks to diverse sugar alcohols, including xylitol, erythritol, mannitol and arabitol. Moreover, metabolic approaches are highlighted that specifically target shortcomings of sugar alcohol production by yeasts from these renewable substrates.

Modulating Oral Delivery and Gastrointestinal Kinetics of Recombinant Proteins via Engineered Fungi

A new modality in microbe-mediated drug delivery has recently emerged wherein genetically engineered microbes are used to locally deliver recombinant therapeutic proteins to the gastrointestinal tract. These engineered microbes are often referred to as live biotherapeutic products (LBPs). Despite advanced genetic engineering and recombinant protein expression approaches, little is known on how to control the spatiotemporal dynamics of LBPs and their secreted therapeutics within the gastrointestinal tract. To date, the fundamental pharmacokinetic analyses for microbe-mediated drug delivery systems have not been described. Here, we explore the pharmacokinetics of an engineered, model protein-secreting Saccharomyces cerevisiae, which serves as an ideal organism for the oral delivery of complex, post-translationally modified proteins. We establish three methods to modulate the pharmacokinetics of an engineered, recombinant protein-secreting fungi system: (i) altering oral dose of engineered fungi, (ii) co-administering antibiotics, and (iii) altering recombinant protein secretion titer. Our findings establish the fundamental pharmacokinetics which will be essential in controlling downstream therapeutic response for this new delivery modality.

Recent advances in microbial production of mannitol: utilization of low-cost substrates, strain development and regulation strategies

Mannitol has been widely used in fine chemicals, pharmaceutical industries, as well as functional foods due to its excellent characteristics, such as antioxidant protecting, regulation of osmotic pressure and non-metabolizable feature. Mannitol can be naturally produced by microorganisms. Compared with chemical manufacturing, microbial production of mannitol provides high yield and convenience in products separation; however the fermentative process has not been widely adopted yet. A major obstacle to microbial production of mannitol under industrial-scale lies in the low economical efficiency, owing to the high cost of fermentation medium, leakage of fructose, low mannitol productivity. In this review, recent advances in improving the economical efficiency of microbial production of mannitol were reviewed, including utilization of low-cost substrates, strain development for high mannitol yield and process regulation strategies for high productivity.

Challenges in enzymatic route of mannitol production

Mannitol is an important biochemical often used as medicine and in food sector, yet its biotechnological is not preffered in Industry for large scale production, which may be due to the multistep mechanism involved in hydrogenation and reduction. This paper is a comparative preview covering present chemical and biotechnological approaches existing today for mannitol production at industrial scale. Biotechnological routes are suitable for adaptation at industrial level for mannitol production, and whatever concerns are there had been discussed in detail, namely, raw materials, broad range of enzymes with high activity at elevated temperature suitable for use in reactor, cofactor limitation, reduced by-product formation, end product inhibition, and reduced utilization of mannitol for enhancing the yield with maximum volumetric productivity.

Genomic analysis of PIS1 gene expression

The Saccharomyces cerevisiae PIS1 gene is essential and required for the final step in the de novo synthesis of phosphatidylinositol. Transcription of the PIS1 gene is uncoupled from the factors that regulate other yeast phospholipid biosynthetic genes. Most of the phospholipid biosynthetic genes are regulated in response to inositol and choline via a regulatory circuit that includes the Ino2p:Ino4p activator complex and the Opi1p repressor. PIS1 is regulated in response to carbon source and anaerobic growth conditions. Both of these regulatory responses are modest, which is not entirely surprising since PIS1 is essential. However, even modest regulation of PIS1 expression has been shown to affect phosphatidylinositol metabolism and to affect cell cycle progression. This prompted the present study, which employed a genomic screen, database mining, and more traditional promoter analysis to identify genes that affect PIS1 expression. A screen of the viable yeast deletion set identified 120 genes that affect expression of a PIS1-lacZ reporter. The gene set included several peroxisomal genes, silencing genes, and transcription factors. Factors suggested by database mining, such as Pho2 and Yfl044c, were also found to affect PIS1-lacZ expression. A PIS1 promoter deletion study identified an upstream regulatory sequence element that was required for carbon source regulation located downstream of three previously defined upstream activation sequence elements. Collectively, these studies demonstrate how a collection of genomic and traditional strategies can be implemented to identify a set of genes that affect the regulation of an essential gene.