Discrimination of Saccharomyces cerevisiae and Saccharomyces paradoxus strains by the SUC2 gene sequences

A 2-Deoxyglucose-Resistant Mutant of Saccharomyces cerevisiae Shows Enhanced Maltose Fermentative Ability by the Activation of MAL Genes

Saccharomyces cerevisiae MCD4 is a 2-deoxyglucose (2-DOG)-resistant mutant derived from the wild-type strain, AK46, wherein the 2-DOG resistance improves the maltose fermentative ability. In the MAL gene cluster, mutations were detected in MAL11 and MAL31, which encode maltose permeases, and in MAL13 and MAL33, which encode transcriptional activators. In maltose medium, the expression of MAL11 and MAL31 in MCD4 was 2.1 and 4.2 times significantly higher than that in AK46, respectively. Besides, the expression of MAL13 and MAL33 also tended to be higher than that of AK46. Although no mutations were found in MAL12 and MAL32 (which encode α-glucosidases), their expression was significantly higher (4.9 and 4.4 times, respectively) than that in AK46. Since the expression of major catabolite repression-related genes did not show significant differences between MCD4 and AK46, these results showed that the higher maltose fermentative ability of MCD4 is due to the activation of MAL genes encoding two maltose permeases and two α-glucosidases.

Sucrose and Saccharomyces cerevisiae: a relationship most sweet

Sucrose is an abundant, readily available and inexpensive substrate for industrial biotechnology processes and its use is demonstrated with much success in the production of fuel ethanol in Brazil. Saccharomyces cerevisiae, which naturally evolved to efficiently consume sugars such as sucrose, is one of the most important cell factories due to its robustness, stress tolerance, genetic accessibility, simple nutrient requirements and long history as an industrial workhorse. This minireview is focused on sucrose metabolism in S. cerevisiae, a rather unexplored subject in the scientific literature. An analysis of sucrose availability in nature and yeast sugar metabolism was performed, in order to understand the molecular background that makes S. cerevisiae consume this sugar efficiently. A historical overview on the use of sucrose and S. cerevisiae by humans is also presented considering sugarcane and sugarbeet as the main sources of this carbohydrate. Physiological aspects of sucrose consumption are compared with those concerning other economically relevant sugars. Also, metabolic engineering efforts to alter sucrose catabolism are presented in a chronological manner. In spite of its extensive use in yeast-based industries, a lot of basic and applied research on sucrose metabolism is imperative, mainly in fields such as genetics, physiology and metabolic engineering.

Invertase Suc2-mediated inulin catabolism is regulated at the transcript level in Saccharomyces cerevisiae

Background

Invertase Suc2 was recently identified as a key hydrolase for inulin catabolism in Saccharomyces cerevisiae, whereas the Suc2 activity degrading inulin varies greatly in different S. cerevisiae strains. The molecular mechanism causing such variation remained obscure. The aim of this study is to investigate how Suc2 activity is regulated in S. cerevisiae.

Results

The effect of SUC2 expression level on inulin hydrolysis was investigated by introducing different SUC2 genes or their corresponding promoters in S. cerevisiae strain BY4741 that can only weakly catabolize inulin. Both inulinase and invertase activities were increased with the rising SUC2 expression level. Variation in the promoter sequence has an obvious effect on the transcript level of the SUC2 gene. It was also found that the high expression level of SUC2 was beneficial to inulin degradation and ethanol yield.

Conclusions

Suc2-mediated inulin catabolism is regulated at transcript level in S. cerevisiae. Our work should be valuable for engineering advanced yeast strains in application of inulin for ethanol production.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-015-0243-3) contains supplementary material, which is available to authorized users.