Identification And Volatile Characteristics Of An Aromatic Yeast

Geotrichum candidum is an important microorganism with multi-purpose. It has been widely used in food, medicine, environmental restoration and so on. G. candidum is also an important aromatic microorganism. However, few studies on the characteristics of flavor material composition and the application of this microorganism in tobacco have been conducted. This paper was focused on an aromatic endophytic bacterial strain named13-1, which was isolated from fresh tobacco leaves. Firstly, the taxonomic identification of the strain was carried out by combination of morphological observation, physiological parameters and phylogenetic analysis. Secondly, volatile components of strain13-1were identified by SPME-GC/MS method. Thirdly, the relationship beween lipase activity and esters volatile compound produced by strain13-1was determined. Fourthly, the changes of flavor compositions in tobacco leaf before and after fermentation by strain13-1were investigated, and meanwhile, the effect on the content and the type of flavor compounds in tobacco leaf after fermentation by strain13-1was evaluated. The main results obtained are as follows:1. Based on morphological, physiological and biochemical characteristics and phylogenetic analysis of26S rDNA gene sequence, the strain13-1was identified as Geotrichum candidum.2. G. candidum13-1strain could produce28volatile compounds of ester and5volatile compounds of alcohols, which including18flavor components such as ethyl caproate (Area:31.91%), ethyl propionate (21.10%), ethyl acetate (9.64%) and phenethyl alcohol (12.21%).3. G. candidum13-1strain exhibited lipase activity, and its lipase gene encoding a conserved region of1,582bp. Totally,16substances concerning carbon, nitrogen, inorganic salts, special factors and so on, were evaluated on effects of the synthetic and hydrolytic activity of lipase of the13-1strain. Among the16substances, molasses vesting in carbon source showed the maximum of promotion effect on the hydrolytic activity of lipase (1632U). Olive oil and glycerin displayed the greatest impact on synthetic activity of lipase with the activity reached352U and388U, respectively. Correlation and linear regression analysis showed that there were significant linear correlation relationship between the synthetic activity of the lipase and the relative content of volatile substances (P=0.89, Sig.=0.00), as well as the number of species (P=0.78, Sig.=0.00), which indicated lipase was proposed to be one of the key influencing factors on ester volatiles produced by13-1strain.4. The content of reducing sugar, polyphenols, carotenoids and other flavor precursors in tobacco leaf could be significantly reduced after fermentation by13-1strain, at the same time, some important volatile flavor components could be produced which inclyuding methyl caproate, methyl caprylate, methyl benzoate, methyl decanoate acid esters, phenylacetic acid methyl ester, beta-damascenone, guaiacol, isoamyl alcohol, linalool and pyridine. This result suggested that13-1strain had the application potential in tobacco to improve flavor.