Screening Of A 2-phenylethanol Producing Fungus And Studying Its Application Of The Rice Wine Fermentation

Microbial biotransformation has the characteristics of high efficiency and litter pollution,the substance synthesized by this method usually regarded as natural and green.Mucor indicus,a non-pathogenic dimorphic zygomycetes fungus,is used for production of several beers and foods.Nowdays,production of ethanol,chitosan and ?-linolentic acid has become a hot research areas for microbial biotransformation in M.indicus.However,the ability of M.indicus to produce 2-phenylethanol(2-PE)has been less reported.Therefore,the aim of this project was to screen M.indicus strains,study the bioconversion of 2-PE and fermentation of rice wine.In this study,the flavor producing strain which named S02 was screened from traditional type Qu.The strain was identified as Mucor indicus by molecular identification of 18 S r RNA and ITS sequence analysis which combined with morphology.Headspace solid-phase microextraction technology(HS-SPME)and Gas Chromatograph-Mass Spectrometer(GC/MS)were used to analysis the volatile flavor compounds in the fermented supernatant fluid.Surprisingly,the analysis shows that M.indicus can be synthesis of 2-PE.When L-phenylalanine(L-Phe)was added into the medium,the 2-PE concentration increased a lot according to the HPLC analysis.With 80 g/L glucose and 6 g/L L-Phe supplemented in the potato hydrolysate medium,and incubated at 30°C and 180 rpm for 84 h,the 2-PE concentration could reach 1.48 g/L.The morphology of M.indicus transited filamentous to yeast-like stimulated by high sugar concentration and 2-PE accumulation,and the yeast-like conductive to 2-PE synthesis.In the application of M.indicus as starter culture fermentation of rice wine,we added the starter culture into the commercial type Qu and assess the rice wine quality by sensory evaluation and chemical compositions.The sensory evaluation results show that the optimized proportion between M.indicus starter and commercial type Qu was 6:4.The change of chemical and flavor compounds were investigated by HS-SPME-GC/MS and HPLC.It was noted that chemical and flavor compounds in the rice wine change a lot.The results as following: ethanol content of the wine increased by 10%,characteristic aroma substance 2-PE content increased by 43%,volatile compounds including easters and alcohols increased by 14% and 25% respectively,critric,pyruvic,lactic and acetic acids increased by 11%,30%,43% and 15% respectively,while succinic acid declined 20%,sweet taste amino acids increased,and the rest test(bitter,umami and acerbity)amino acids decreased in the end.Our study showed that M.indicus as starter culture fermentation of rice wine enhanced the concentrations of flavor compounds which provided an idea for upgrade the starter tablet technology for the rice wine manufacture.