| Glyceric acid?GA?is a kind of organic acid,which widely exists in all kinds of plants in nature.Its derivatives also exist in the body as a metabolite.GA has many applications in chemical,medical,food,and so on.In this work,the fermentation and extraction process for converting glycerol to produce glyceric acid by Gluconobacter japonicus HD1025.The fermentation conditions of the shake flask were optimized.The optimum culture conditions were:culture temperature 31?,shaking speed 220 rpm,initial pH 6.0,liquid volume 30 mL,and inoculum 10%.Amplification experiments of a 5 L fermentor were carried out and the results showed that the pH of the fermentation process was controlled to 5 by using NaOH.The fermentation efficiency was better under the condition of 10%dissolved oxygen control.A validation test was carried out using a 30 L fermentor and the results showed that the highest concentration of glyceric acid reached 73.17 g/L when cultured in medium containing 150 g/L glycerol as carbon source and when the air flow rate and agitation speed were controlled at 0.8 vvm and 300 rpm,the pH value was 5 and the dissolved oxygen was controlled at 10%.In this work,the effect of transformation conditions on transformation efficiency in the production of glyceric acid by resting cell transformation was studied.Based on the single factor experiment,the response surface experiment design was carried out.The results showed that the yield of glyceric acid reached 64.27 g/L under the optimal conditions of 2.05%biomass concentration,143.24 g/L substrate glycerol concentration and 30.4?culture temperature.Experiments were carried out on resting cell recyclability and transformation stability.The results showed that in the six batches of continuous transformation,the resting cells had relatively stable glycerate production in the first four batches,and the conversion rate was also maintained at 70-90%,the average volume yield reached 1.15 g-1·L·h-1.Immobilized cells technology was used to product glyceric acid by converting glycerol.The orthogonal methodology was used to optimize the conditions for preparing immobilized cells.It is found that the optimal experimental conditions was the concentration of resting cells 10%,the concentration of sodium alginate 1%,and the concentration of carrageenan 0.4%.Under these conditions,the yield of glyceric acid reached 46.87 g/L.The experiment determined the optimal conditions for the growth of acid for immobilized cells.It was temperature 30?,pH value 5 and the substrate concentration 150 g/L.The production curves of immobilized cells and resting cells were compared.The results showed that resting cells have good stability and can maintain high enzyme activity during continuous transformation for three generations,which is more advantageous than immobilized cells.A separation and extraction route of glyceric acid was developed.The fermentation removal of protein using a nanofiltration membrane after deal with ceramic membrane,subjected to decoloring treatment with activated carbon.The boutique calcium glycerate of content of 99.1%was obtained by concentrating and crystallization,vacuumly desiccating after repeated crystallization.The cost of producing and extracting 1ton of calcium glycerate was about 36,000 yuan,which has good industrial application prospects. |
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