| Sophorolipids(SLs)is a kind of secondary metabolite of yeast and can be obtained by fermentation process under certain conditions with sugar and vegetable oil as carbon sources.As a kind of glycolipid,biosurfactant of SLs has general properties of conventional surfactants,such as solubilization,emulsification,wetting,foaming,dispersion and surface tension reduction.It also has characteristics of non-toxicity,biodegradability,high temperature and salt tolerance,wide p H range adaptability and environmentally friendly.Based above-mentioned characteristics,SLs could be used in the fields of petroleum,environmental protection,medicine,food,cosmetics,home care,agriculture and others.And SLs has been reported to have great potential to partially or completely replace chemically synthesized surfactants.Factors such as higher production costs,more complex components,and lower added value in applications have limited the large-scale application of SLs to a certain extent.Therefore,in order to reduce the production cost of SLs and enable them to be industrially produced,this article focuses on how to improve the yield and quality of SLs.This article focuses on medium optimization,fermentation process optimization,separation method optimization,and production mode transformation.The fermentation process and scale-up of SLs were systematically studied in terms of trial scale-up process.By analyzing the data obtained from the shake bottle level,50 L bioreactor scale and pilot scale,the following conclusions are drawn:1.The effects of industrial grade and reagent grade of glucose and industrial grade and edible grade of fatty acid on the production of SLs were evaluated.The results showed that the type of carbon source has no obvious effect on the fermentation of SLs.Based on cost and yield considerations,industrial grade glucose and oleic acid could be selected as carbon sources for SLs production.2.The effects of seed passage number and inoculum amount on the production of SLs were investigated.The results revealed that both passage number of yeast and inoculum dose significantly affect the production of SLs.Compared to the cells with high passages,the production of lactonic SL by the cells with low passages was increased by181.0%,and the production of total SL was increased by 61.5%.The scale-up production data showed that high inoculum dose of 10% could accelerate the fermentation into SLs accumulation period,thereby to shorten the fermentation period.Although the increase of inoculum dose had little effect on total SLs production,it was beneficial to the accumulation of lactonic SLs.3.The effects of fermentation time and nitrogen source on the production of SLs were also investigated.The extension of fermentation time and the substitution of nitrogen source of peanut meal could significantly increase lactonic SLs production.4.The fermentation broth of SLs can be pretreated and the subsequent products can be separated and purified by natural sedimentation-plate and frame filtration-resin adsorption-ultrafiltration and nanofiltration concentration.After process optimization,the lactonic SLs with a purity of 84.47% and the acidic SL with a purity of 99.46% were obtained.In addition,the separation and purification process could reduce or eliminate the use of organic reagents,subsequently improve the safety and environmental protection of SLs production.5.Finally,the scale-up effects of the pilot-scale and industrial production of SLs were evaluated.The data of the pilot scale-up test showed that the production of total SLs has been significantly improved.In general,the small test results of the 50 L fermentor can be achieved in the 39.2T pilot test.In addition,complex nitrogen source composed by oybean flour,corn pulp and peanut cake flour was more suitable for SLs production in pilot scale.The use of complex nitrogen source could not only further reduce the production cost of SLs,but also improve the yield of lactonic SLs,and thus enhance the market competitiveness of SLs. |
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