Expression of monellin in a food-grade delivery system in Saccharomyces cerevisiae.
BACKGROUND
Genetically modified (GM) foods have caused much controversy. Construction of a food-grade delivery system is a desirable technique with presumptive impact on industrial applications from the perspective of bio-safety. The aim of this study was to construct a food-grade delivery system for Saccharomyces cerevisiae and to study the expression of monellin from the berries of the West African forest plant Dioscoreophyllum cumminsii in this system.


RESULTS
A food-grade system for S. cerevisiae was constructed based on ribosomal DNA (rDNA)-mediated homologous recombination to enable high-copy-number integration of the expression cassette inserted into the rDNA locus. A copper resistance gene (CUP1) was used as the selection marker for yeast transformation. Because variants of transformants containing different copy numbers at the CUP1 locus can be readily selected after growth in the presence of elevated copper levels, we suggest that this system would prove useful in the generation of tandemly iterated gene clusters. Using this food-grade system, a single-chain monellin gene was heterologously expressed. The yield of monellin reached a maximum of 675 mg L(-1) .


CONCLUSIONS
This system harbors exclusively S. cerevisiae DNA with no antibiotic resistance genes, and it should therefore be appropriate for safe use in the food industry. Monellin was shown to be expressed in this food-grade delivery system. To our knowledge, this is the first report so far on expression of monellin in a food-grade expression system in S. cerevisiae.
School of Biology and Pharmaceutical Engineering, Wuhan Polytechnic University, Wuhan 430023, China.
Jun
J
Liu
School of Biology and Pharmaceutical Engineering, Wuhan Polytechnic University, Wuhan 430023, China.
Da-zhong
DZ
Yan
School of Animal science and Nutritional Engineering, Wuhan Polytechnic University, Wuhan 430023, China.
Sheng-jun
SJ
Zhao
D000354:Africa, Western; D004271:DNA, Fungal; D004275:DNA, Ribosomal; D005524:Food Technology; D005638:Fruit / Q000737:chemistry; D015870:Gene Expression; D017343:Genes, Plant; D006801:Humans; D029583:Menispermaceae / Q000737:chemistry*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D013549:Sweetening Agents; D014170:Transformation, Genetic
D004271:DNA, Fungal; D004275:DNA, Ribosomal; D010940:Plant Proteins; D013549:Sweetening Agents
CUP1 gene; S. cerevisiae; food-grade system; monellin; ribosomal DNA