| Liamocin is a kind of active polyol ester substance with higher density than water,which has a variety of biological activities.After hydrolysis,it can be further prepared into biofuel and industrial raw materials.It is widely used in medicine,food,biological control and so on.Liamocin can be obtained by biosynthesis and secreted directly into the extracellular system by Aureobasidium pullulans.As an oil-producing microorganism.The types of carbon and nitrogen sources directly affect the production of liamocin,and the use of natural carbon and nitrogen sources can significantly reduce the production cost of liamocin,and is conducive to the realization of the double carbon target.This study uses cheap biomass as raw material to prepare liamocin,aiming at providing application and theoretical basis for effective utilization of biomass resources and preparation of biofuel.Specific operations and results are as follows:1.By fermenting and culturing A.pullulans under monosaccharide and mixed sugar conditions,the effect of a single inhibitor on the strain was determined,and then the fermentation environment in which multiple inhibitors coexist in corn straw hydrolysate was simulated.The single factor experimental results indicate that the higher the inhibitor concentration,the greater the inhibitory effect on the bacterial strain,and the lower the liamocin production.When the concentration of acetic acid is greater than 1.5 g/L,and the concentration of furfural and phenol is greater than 1 g/L,bacterial growth is completely inhibited.When simulating corn straw hydrolysate,due to the synergistic effect between composite inhibitors,no liamocin was produced,and the synergistic effect of the inhibitors was greater than that of a single inhibitor.2.The fermentation results of corn straw hydrolysate show that: After detoxification treatment of corn straw hydrolysate,the carbon source content in the hydrolysate is relatively low,and the presence of inhibitors still inhibits bacterial fermentation,and corn straw hydrolysate has little impact on bacterial growth,but liamocin production is greatly limited.Only by diluting the corn straw hydrolysate 1000 times can the inhibitor content not have an inhibitory effect on oil synthesis.3.When using small molecules and oligosaccharide as carbon sources,malt juice,molasses,cellobiose and cyclodextrin are not suitable as carbon sources for the fermentation of A.pullulans to produce liamocin.The liamocin yield of maltose was only0.88% lower than that of the control group.It can be used as a carbon source instead of glucose.4.When natural polymers such as starch,cellulose,inulin,and chitosan are used as carbon sources,the results show that: Starch,cellulose,chitosan and cyclodextrin are not high quality carbon sources available to strains.When using inulin as a carbon source for fermentation to produce liamocin,the yield of fully hydrolyzed inulin liamocin increased by 262.21% compared to the control group.inulin as a carbon source has great potential in the fermentation process of producing liamocin by A.pullulans.5.When using corn slurry dry powder,soybean meal cake,peanut meal cake,gelatin,urea,etc.as nitrogen sources instead of yeast extract,the results show that: When using peanut meal and soybean meal as nitrogen sources for fermentation,the yield of liamocin increased.However,when using corn slurry dry powder,gelatin,and urea as nitrogen sources for fermentation,the yield of liamocin decreased to varying degrees.The most suitable high-quality nitrogen sources for producing liamocin by A.pullulans fermentation in this study are soybean meal cake and peanut meal cake.Research has shown that in order for A.pullulans to convert corn straw and other straw crops into products with high added value,it is necessary to further optimize the detoxification process of corn straw hydrolysate to ensure that the inhibitor content in the hydrolysate does not affect the production of liamocin by Aspergillus pullulans.When using natural polymers as carbon sources for fermentation,inulin and cellulose as carbon sources have great potential in the production of liamocin by A.pullulans fermentation,making them high-quality natural polymer raw materials that can be utilized by strains.When using different types of nitrogen sources instead of yeast extract for fermentation,the most suitable high-quality nitrogen sources for producing liamocin by A.pullulans fermentation are soybean meal cake and peanut meal cake. |
