| Propionic acid is an ideal food preservative and an important fine chemical raw material.As the concept of people is now improving,the requirements for green food and natural antisepsis are getting higher and higher.The production of propionic acid by the biological fermentation method has received more and more attention,and the development is getting faster and faster.At present,the research on the production of propionic acid by fermentation method mainly focuses on the laboratory and the small-scale experimental stage.The industrial amplification and achievement conversion rate are not high,and there are also many problems in the extraction process.Microbial fermentation is a complex process.Any change in the process of amplification can cause complex changes in the fermentation process.The growth of Propionibacterium acid-producing bacteria requires certain nutrients and culture conditions.After the fermentation is completed,the fermentation broth will contain residual nutrients and microbial metabolites.Propionic acid extracted from the fermentation broth requires the separation and decolorization of propionic acid to increase its purity and product color.Therefore,it is an urgent problem to establish a process route for the production of propionic acid which is economical and efficient and whose purity meets the applicable standards.In this thesis,the predecessors of this laboratory researched the production of propionic acid by fermentation of propionic acid,and scaled up the scale of the fermentation step by step.During the amplification process,a systematic optimization and improvement of the fermentation process was explored.Industrial route for the industrial production of propionic acid by fermentation,followed by distillation,ion exchange,activated carbon decolorization and other methods,according to the characteristics of different methods to establish an extraction and preparation of high-purity propionic acid extraction process.The main research of the paper is as follows.1.Study on Pilot Production of Calcium Propionate by Propionic Acid-producing Bacillus Fermentation.Based on the optimized fermentation process in this laboratory,the advantages and disadvantages of batch fermentation and fed batch fermentation were further compared.The fermentation scale was expanded from shake flask culture to 7L tank fermentor culture,and then fermented in 150L tanks and 2T tanks.Cultivation,further optimization and adjustment of the production of propionic acid fermentation process.1)In the comparison of fermentation methods,the methods of batch fermentation and fed batch fermentation have their advantages and disadvantages.The final acid production in the batch fermentation process is lower than that in batch fed,because the initial concentration of glucose and corn steeps in batch fermentation is relatively high,and the production of Propionibacterium acidophilus is inhibited.The acidity is slightly lower,but there is no need for feeding during the fermentation process,which reduces the possibility of contamination,and the operation is simple.This is the advantage of batch fermentation;the final acid production concentration in fed batch fermentation mode is higher than the batch fermentation.About%,but the operation is relatively complex,considering the need to measure the level of fermentation and industrial scale up,select the culture method with high acid production as the main training method.2)The scale of fermentation was expanded from 500 ml shake flask culture to 7 L tank fermentation,and then scaled up to 150 L tanks,and finally enlarged to 2 T tanks for small-scale production of fermentation culture.Through a step-by-step scale-up culture,a process route was continuously optimized and adjusted.The level of fermentation is mainly measured by the total amount of acid produced,the conversion rate of sugar and acid,and the production efficiency.Therefore,these relevant indicators are determined at different fermentation scales.Compared with shake flask culture,fermenter culture has the advantages of real-time pH control,uniform dispersion of bacteria,and rapid growth of bacteria.As a result,acid production is increased,conversion rate of sugar and acid is higher,and fermentation cycle is shortened.A process route that can be used directly for the production of propionic acid by industrial fermentation is optimized.This process route produces 39.67g.L-1acidity,0.461g.g-11 sugar acid conversion rate and 0.331g·L-1·h-11 production efficiency in the small-scale 2T scale fermentation.The fermentation level does not reach the highest level and needs further development.Optimization.2.Extraction and preparation of high-purity propionic acidAn extraction process for preparing high-purity propionic acid by ion exchange method,distillation and concentration method,active carbon decoloration method,and calcium salt precipitation method is established,and the main results are as follows.1)Use 001x7H H-type resin to replace ammonium ions and other cations in fermentation broth with hydrogen ions using ion exchange method to achieve acidification of the fermentation broth.The amount of acidified treatment of 001x7H type H resin was 3 times of the volume of the resin,and the pH of the fermentation solution after acidification could reach 2.35.Distillation can distill propionate from acidified fermentation broth.The best distillation conditions are temperature 60°C,vacuum degree-0.1 MPa,rotation speed 27r/min,evaporation efficiency 1.2L/h,concentration of propionic acid distilled out and fermentation The concentration of propionic acid in the liquid was flat,and the spray-dried product had a calcium propionate content of 82.38%and a pure white color.2)Using activated carbon to decolorize the fermentation broth,it was found that the main factors affecting the decolorization effect were the amount of activated carbon,the decolorization temperature and the decolorization time.The adsorption of activated carbon had little effect on the loss of propionic acid,and the retention rate of propionic acid was basically maintained above 85%.The optimum decolorization process obtained by orthogonal test is 2.0%activated carbon,temperature 50°C,and decolorization time 90 min.The solubility of calcium propionate is greater than the solubility of certain organic acid salts in the fermentation broth.The use of the calcium salt precipitation method removes certain organic acids from the fermentation broth to achieve further purification.After purified by activated carbon decoloration and calcium salt precipitation,the calcium propionate content of the product was 54.14%,and the color was white or light yellow.3)According to the optimized propionic acid conditions of the fermentation broth and decolorization conditions of the activated carbon,the process for extracting propionic acid from the fermentation broth is further optimized and adjusted,and the decolorization process of the activated carbon is adjusted to the concentration of the fermentation broth.After adjustment,the use of the activated carbon is reduced.For the original 20%-30%,and good decolorization effect.In addition,after activated carbon adsorption,the separation and concentration of activated carbon are combined into one step,simplifying the entire process route.The use of calcium salt precipitation method removes some of the organic acids in the fermentation broth for further purification.After purified by activated carbon decolorization and calcium salt precipitation,the calcium propionate content of the product was 62.35%,and the color was white or light yellow. |
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