Adaptability Of Aspergillus Cristatum Strain FZ-2 To Dry Environment And Its Metabolism

By modifying the known amounts of glycerol in agar media,we investigated the effects of water activity(aw)and temperature on the rates of mycelial growth,conidia formation,germination,and colony characteristics of Aspergillus cristatum.Based on the morphology and fungal ITS analysis,the result showed that strain FZ-2,which can grow,sporulate,and germinate well under low aw and high temperature environment was identified as Aspergillus cristatum.The optimum aw for strain FZ-2 growth was 0.95-0.90,the range of aw values permitting conidia formation was from 0.95 to 0.77,with the optimum aw 0.83,and the optimal aw for conidia germination was from 0.95 to 0.87.Strain FZ-2 had shown optimal growth over a relatively wider range of temperature from 28 ? to 37? The temperature range for spore formation was from 20 ? to 37?,with the optimum 37?.The optimal temperature for spore germination was from 25 ? to 33 ?.We also observed colony morphology changes under different aw and temperature conditions.And the effect of water activity on the growth of strain FZ-2 was more pronounced than that of temperature.On this basis,The effects of water activity(aw)on the metabolism of strain FZ-2 were analyzed by gas chromatography-mass spectrometry,It was found that fatty acids account for a high proportion of the active ingredients detected.The lipid production of strain FZ-2 under different aw conditions were further analysis by thermal-acid method,The optimum aw for strain FZ-2 lipid production was 0.95,under the optimum aw,the cell biomass and lipid productivity were higher than that of other aw conditions(0.99 and 0.83).Under optimum water activity,lipid productivity of strain FZ-2 reached the maximum value of 28.09%and 1.07 g/L on the 7th and 10th day of fermentation,respectively.The changes of aroma compounds of green tea were determined by headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry,and the changes of total soluble sugar content,free amino acids content,tea polyphone content were also analyzed,The results showed that the biotransformation of Aspergillus cristatum can change the aroma and chemical composition of green tea water.