Stable N-acetyltransferase Mpr1 improves ethanol productivity in the sake yeast Saccharomyces cerevisiae

Expression, optimization and biological activity analysis of recombinant type III collagen in Komagataella phaffii

Type III collagen, a fundamental constituent of the extracellular matrix (ECM), is extensively utilized across the biomedicine, tissue engineering, and cosmetic industries because of its exceptional biocompatibility and biodegradability. Despite its widespread application, traditional methods of collagen production are often hindered by the limit yield, potential immunogenicity, and batch-to-batch variability. In the present study, we describe a synthetic biological approach for expressing full-length recombinant type III collagen (RCIII) in the Komagataella phaffii system. Furthermore, the protein expression level was effectively increased by co-expression of the MPR1 gene, which improved the intrinsic antioxidant defenses of yeast cells, thereby reducing oxidative stress damage. The resulting RCIII maintains its native secondary structure and exhibits robust biological activities, including the promotion of platelet coagulation, enhancement of cell migration, and anti-inflammatory efficacy. Our findings suggest a viable pathway for large-scale, industrial production of type III collagen, offering a promising biomaterial for advanced biomedical applications, and contributing to the circular economy of the biomedical sector.

Characterization and application of Lachancea thermotolerans isolates for sake brewing

Non-conventional yeasts are increasingly being used in the production of fermented beverages owing to their ability to create unique and high-quality products. The yeast Lachancea thermotolerans is of great industrial significance, particularly in the production of l(+)-lactic acid, which is beneficial for acidifying wine, beer, and potentially sake. To explore its potential in sake brewing, three L. thermotolerans strains were isolated from natural environments and their physiological and fermentative characteristics were examined. The isolates surpassed the L. thermotolerans type strain (NBRC 1985) in lactic acid production under various culture conditions and exhibited comparable growth rates to that of Saccharomyces cerevisiae at 15-20 °C. Sake brewing tests using these isolates yielded approximately 3500 ppm of lactic acid, with a slightly lower production of aroma components compared to that produced by sake yeast, and an ethanol content of approximately 11-12 % was obtained. Reverse transcription-quantitative polymerase chain reaction revealed variable expression in putative lactate dehydrogenase genes depending on the culture conditions. Our findings suggest that L. thermotolerans strains can be used in sake brewing to produce unique sake.

Recent developments in horizontal gene transfer with the adaptive innovation of fermented foods

Horizontal gene transfer (HGT) has contributed significantly to the adaptability of bacteria, yeast and mold in fermented foods, whose evidence has been found in several fermented foods. Although not every HGT has biological significance, it plays an important role in improving the quality of fermented foods. In this review, how HGT facilitated microbial domestication and adaptive evolution in fermented foods was discussed. HGT can assist in the industrial innovation of fermented foods, and this adaptive evolution strategy can improve the quality of fermented foods. Additionally, the mechanism underlying HGT in fermented foods were analyzed. Furthermore, the critical bottlenecks involved in optimizing HGT during the production of fermented foods and strategies for optimizing HGT were proposed. Finally, the prospect of HGT for promoting the industrial innovation of fermented foods was highlighted. The comprehensive report on HGT in fermented foods provides a new trend for domesticating preferable starters for food fermentation, thus optimizing the quality and improving the industrial production of fermented foods.

Molecular mechanisms and highly functional development for stress tolerance of the yeast Saccharomyces cerevisiae

In response to environmental stress, microorganisms adapt to drastic changes while exerting cellular functions by controlling gene expression, metabolic pathways, enzyme activities, and protein-protein interactions. Microbial cells that undergo a fermentation process are subjected to stresses, such as high temperature, freezing, drying, changes in pH and osmotic pressure, and organic solvents. Combinations of these stresses that continue over long terms often inhibit cells' growth and lead to their death, markedly limiting the useful functions of microorganisms (eg their fermentation ability). Thus, high stress tolerance of cells is required to improve productivity and add value to fermented/brewed foods and biofuels. This review focuses on stress tolerance mechanisms, including l-proline/l-arginine metabolism, ubiquitin system, and transcription factors, and the functional development of the yeast Saccharomyces cerevisiae, which has been used not only in basic science as a model of higher eukaryotes but also in fermentation processes for making alcoholic beverages, food products, and bioethanol.

High-level production of ornithine by expression of the feedback inhibition-insensitive N-acetyl glutamate kinase in the sake yeast Saccharomyces cerevisiae

We previously reported that intracellular proline (Pro) confers tolerance to ethanol on the yeast Saccharomyces cerevisiae. In this study, to improve the ethanol productivity of sake, a traditional Japanese alcoholic beverage, we successfully isolated several Pro-accumulating mutants derived from diploid sake yeast of S. cerevisiae by a conventional mutagenesis. Interestingly, one of them (strain A902-4) produced more than 10-fold greater amounts of ornithine (Orn) and Pro compared to the parent strain (K901). Orn is a non-proteinogenic amino acid and a precursor of both arginine (Arg) and Pro. It has some physiological functions, such as amelioration of negative states such as lassitude and improvement of sleep quality. We also identified a homo-allelic mutation in the ARG5,6 gene encoding the Thr340Ile variant N-acetylglutamate kinase (NAGK) in strain A902-4. The NAGK activity of the Thr340Ile variant was extremely insensitive to feedback inhibition by Arg, leading to intracellular Orn accumulation. This is the first report of the removal of feedback inhibition of NAGK activity in the industrial yeast, leading to high levels of intracellular Orn. Moreover, sake and sake cake brewed with strain A902-4 contained 4-5 times more Orn than those brewed with strain K901. The approach described here could be a practical method for the development of industrial yeast strains with overproduction of Orn.