Optimization Of Culture Conditions For Fermentation Of 5-aminolevulinic Acid By Propionibacterium Freudenrenichii

5-Aminolevulinic acid?ALA?is a precursor of rattletrap compounds,such as heme,chlorophyll,and vitamin B₁₂2 in vivo,with excellent environmental compatibility and selectivity in vitro.High-new light-activated pesticides have broad application prospects.The use of the solution containing less ALA is beneficial to the growth of the plant,and it can enhance the plant's ability to resist the effects of adverse environmental factors.Meanwhile,weeds can be killed using thesolution containing more ALA.In the treatment of diseases,ALA treatment for cancer has been confirmed by many reports.Its light sensitivity is of concern.At this stage,the output of ALA mainly depends on chemical synthesis.As the demand for ALA increases,it is particularly important to find a method that can increase the production of ALA.With the development of metabolic engineering and genetic engineering,the production of ALA by microbial fermentation has gradually replaced the use of chemical methods to produce ALA.In the previous study,ALA was produced on a large scale using the Pro bionic Acid Bacterium?PAB?engineered strain,and the yield of ALA was increased nearly three-fold after high-level expression of hemA derived from red bacteria in PAB.The downstream products were also large.Therefore,in the presentstudy,the production of ALA by intermittently feeding the succinic acid and glycine precursors of ALA was investigated.The single-factor experiment determines the optimal pH and inoculum for ALA production.Response surface analysis was used to further optimize the culture medium.The fermentation broth was filtered through hollow fiber and concentrated by reverse osmosis?yield was 74.2%?.Di?2-ethylhexyl?phosphate,tributyl phosphate,and ethyl acetate were used as extractants,n-hexane as diluent,and hydrochloric acid as the diluent.The stripping agent optimizes the ALA extraction process for PAB fermentation broth.The experimental results showed that Propionibacterium had the best ability to produce ALA when the pH value was 5 during fermentation.The inoculum size of 1.0%Propionibacterium had strong ability to produce ALA.The concentration of succinic acid and glycine added at feed supplementation was 0.02 mol/L and 0.03 mol/L,respectivel,in propionate fermentation to increase ALA production.The response surface methodology was used to optimize the culture medium,and the optimal culture medium components are as follow:glucose content:5.74 g/L;peptone content:6.28 g/L,beef extract content:7.68 g/L.The ALA content in the fermentation broth reached 24.28mg/L after continuous culture for96 hours under the above optimal culture medium conditions.In the purification process of ALA,pure ALA·HCl was obtained by vacuum concentration and crystallization at 65?,and the crystal purity was 97%.The total yield is 60%.In summary,the appropriate conditions for the production of ALA in PAB fermentation were determined and ALA was extracted.Thwsw will provide evidences for future research in this field.