Optimization of succinic acid production from industrial crude glycerol by encapsulated Anaerobiospirillum succinicproducens

Various important chemical precursors in both food and pharmaceutical industries have to depend on a bioproduct such as succinic acid for initiation in the process. This paper studies the optimization of a batch cultivation process for the production of succinic acid from crude glycerol by using Anaerobiospirillum succinicproducens ATCC 29305 encapsulated with sodium cellulose sulfate/poly-dimethyl-diallyl-ammonium chloride.       The batch conditions for the flask were optimized by response surface methodology based on a Box–Behnken design. This design was employed to assess the individual and interactive effects of the four main parameters (pH, crude glycerol concentration, shaking speed and temperature) on succinic acid production under anaerobic conditions. Results from the response surface analysis showed that the data were adequately fitted by a second-order polynomial model via a quadratic regression relationship. The final mathematical model after eliminating the insignificant terms and refining the succinic acid production was quadratic model. For the succinic acid yield it was observed that the interactive effect between crude glycerol and shaking speed was statistically significant. Optimization conditions for maximizing the production were as follows: pH, 6; crude glycerol, 40 g/L; shaking speed, 150 rpm; temperature, 39 ⁰C. Under these conditions the maximal numerical solution of the model gave a predicted succinic acid level of 34.66 g/L. For the flask, the experimental production of succinic acid was 34.80 g/L with a conversion yield (87%), and a ratio of succinic acid to acetic acid (34:1).  Similar experimental results were obtained for the stirred tank bioreactor.