Establishing a bioconversion process for the production of succinic acid using industrial feedstocks.

Abstract

One of the leading challenges of the current global situation is the decline of non-renewable, fossil fuels. Due to this rapid depletion, there is a shift towards replacing petrochemical products with equivalent, ideally superior bio-based substitutes. The bio-chemical of interest that was studied in this work is bio-succinic acid which is considered a platform chemical. Bio-based procedures have the attractive advantage of potentially obtaining a high-value product from an underutilised product/waste stream. In this dissertation, the industry that was focused on was the sugar sector, this vital industry is under pressure it is therefore crucial that alternative revenue avenues are identified. A literature study highlighted the importance of succinic acid, detailed both the upstream and downstream literature methods and addressed the impact that biochemical processes could have within South Africa. Small scale flask studies were conducted using succinate-producing microorganisms, on synthetic C5 and C6 sugar medias, namely xylose and glucose. The results from these studies showed that L. paracasei and C. glutamicum were the top performing strains on the C6 sugar (glucose) media and as a result these strains were then grown on C6 industrial material, namely sugarcane juice and molasses. These flask studies concluded that C. glutamicum grown on molasses was the superior combination, with a succinic acid concentration of 18.81 ± 0.75 g.L-1 and a productivity of 0.67 ± 0.07 g.L-1.hr-1 being achieved. The process was then successfully scaled up to 30L reactors where a succinic acid concentration of 28.89 ± 3.57 g.L-1 was reached, which was higher than the ‘ideal’ glucose reactor run. Downstream processing of the harvested broth was conducted using the precipitation method. Process development was performed, and the final method resulted in a final succinic acid recovery of 54.47 ± 14.02 % and 58.20 ± 2.24 % for the glucose and molasses-based medias respectively. In conclusion, molasses has the potential as an alternative carbon source in the production of succinic acid. The biochemicals sector is still a novel concept within South Africa, and as this platform gains more traction such studies show the ‘value’ of industry’s waste/by-product streams, especially for the sugar industry.