This issue recommends an article by Associate Professor Niu Fuxing's research group from the School of Biological and Chemical Engineering, Guangxi University of Science and Technology, published on Microbial Cell Factors: Key Role of K⁺and Ca²⁺in high-yield ethanol production by S. Cerevisiae from concentrated sugarcane molasses。 This study used atmospheric pressure and room temperature plasma for mutagenesis to screen brewing yeast strains with robust performance against different stress factors (high osmotic pressure, high alcohol content, high temperature, high salt ions, and high concentration of sugarcane molasses). The ethanol synthesis yield of the brewing yeast selected from this with robust performance against high concentration sugarcane molasses has reached the current high level of physical mutagenesis (111.65 g/L, sugar alcohol conversion rate of 95.53%). Finally, by combining the cell morphology, fermentation capacity, and omics analysis of yeast, it was revealed that the main limiting factor that prevents brewing yeast from achieving high concentration sugarcane molasses and high concentration ethanol fermentation is K⁺And Ca²⁺Simultaneously existing impacts.

There are many raw materials for the synthesis of bio based ethanol, and research and development from the perspectives of environmental protection, economy, and prosperity are the focus. China is a populous country, and the amount of sugar consumed each year due to food additives, industrial applications, etc. ranks among the top in the world. Sugarcane is one of the main raw materials for sugar extraction, and at the same time as extracting sugar, it produces molasses. Early research data shows that producing 3 tons of sugar can also produce about 1 ton of molasses. Sugar syrup is a mixture with complex components. Direct discharge or use for field fertilization is wasteful and can cause environmental pollution, and it is also an underutilization of resources. However, utilizing molasses (non grain) biological resources for ethanol synthesis of brewing yeast can continuously meet people's demand for ethanol consumption and promote the development of green and low-carbon energy in the country. The process of using molasses for ethanol fermentation by brewing yeast is relatively mature, but the efficiency of producing high concentration ethanol using high concentration molasses is a challenge, which is due to the influence of various coercive factors. However, from the perspective of scientific research, there has been no research report on which is the key limiting factor.

Researchers utilized ARTP (room temperature plasma) mutagenesis, adaptive evolution, and high-throughput methods based on triphenyl-2H-tetrazolium chloride (TTC) and precursor pyruvic acid (or pyruvic acid radical ion) with Fe³⁺Double high-throughput screening method with yellow color after complexation reaction (Py Fe)³⁺）Obtained high temperature (37 ℃), high alcohol (10%), high osmotic pressure (400 g/L fermentable total sugar), and high concentration K for high concentration sugarcane molasses (total sugar concentration up to 300 g/L) and sucrose addition models, respectively⁺(15 g/L)、Ca²⁺(8 g/L)、K⁺&Ca²⁺Seven robust brewing yeast strains under fermentation conditions of 15 g/L&8 g/L (Figure 1, Table 1). By comparing the cell morphology of each robust strain in a high concentration sugarcane molasses environment (Figure 2), the yield and number of cells involved in ethanol synthesis (Figures 3 and 4), and conducting comparative genomics, transcriptomics GO, and KEGG analysis on the robust strains, K was determined⁺、Ca²⁺The simultaneous existence is the main factor limiting the high concentration sugarcane molasses ethanol fermentation of brewing yeast.

Table 1 Yield difference compared to wild-type J108 under the same fermentation conditions

Figure 2 Cell morphology of different strains fermented with 250 g/L molasses

Figure 4. Using 250 g/L sugarcane molasses fermentation in a 5L fermenter system, the ethanol production of strain NGTM-F1 reached 111.65 g/L