Studies On Low-cost And High-density Culture And The Preservation Of Rhodopseudomonas Palustris

Rhodopseudomonas palustris,belongying to Rhodospirillaceae,Rhodopseudomonas genus,is one of the most extensively studied and application photosynthetic bacteria.R.palustris is one of microbial feed additives which has been approved to be by ministry of agriculture.R.palustris has been widely used in aquaculture,feed industry,sewage dispoal and other purposes,and has showed great econimical,ecological and social benefits.Microbial agents demands heavily,but the lacking of regulation lead to industry chaos.At present,microbial agents for aquaculture have some problems such as high price,low number of viable cells,poor product stability,time-critical shelf lives.This experiment chooses cheaper agricultural by products as the main nutrition of fermentation to culture R.palustris,and optimize culture conditions,simplify microbial agents preparation procedures,optimize preservation conditions,which aims to reduce the production of cost and benefits the popularization.It will provide some reference basises for some liquid microbial agents to be commercialization.This part was under the condition of 500mL flask.Beginging with choosing the main nutrition of fermentation to culture R.palustris from agricultural products through the signal factor experiment.The most suitable medium for living cells production was formulated with the ingredients:molasses 9g/L?peanut meal 5g/L?KH₂PO₄ 1.0g/L?Na₂HPO₄ 1.0g/L?MgCl₂ 2.0g/L?NaCl 2.0g/L?CaCl₂0.2g/L?FeCl₃ 0.02g/L?yeast extract power 0.5g/L,which through orthogonal test.The favorable fermentation condition was determined:initial pH value of medium 6.8,seed volume 6%,fermentation temperature 37?,sharking speed 100r/min.The number of living cells was enhanced,reaching 3.96×10⁹CFU/mL within 48 hours.Refer the results of sharking flask,further research the conditions for cultureR.palustris in 5L fermentor.The optimal conditions were that pH 6.8,stirring rate 300r/min,aeration rate2L/min,and choose acetic acid,sodium carbonate for neutralizing agents.Under the optimized conditions,the living cells could reach about 6.43×10⁹cfu/mL after 36 hours.Comparing with the shaking flask test,the living cells rose 62.3%,futhermore,the culture cycle could shorten 12hours.Optimization of centrifugal conditions of fermentation broth,the result showed that the best method of centrifuge was maintaining 10min under 8000r/min condition,harvesting rate about81.5%.The next content research the influence of liquid microbial agents preservation from different pH conditions and glycerol contents level.It shown that the hightest bacterial survial rate was up to 6%after fifteen weeks under the conditions of pH5.0⁶.0,glycerol contents 0¹%.