(465c) Phenotypic Adaptation of a Novel Bacterium for a Low-Cost Production of D-Lactic Acid

Authors: 
Thongchul, N., Chulalongkorn University
Thitiprasert, S., Chulalongkorn University
Limsampancharoen, S., Chulalongkorn University
Toliang, W., Chulalongkorn University
In bioplastic industry, we can divide the processing technology into 3 catergories including upstream, intermediate, and downstream processes. In the upstream process, we can subcategorize into 3 main steps, i.e., feedstocks pretreatment, fermentation, and downstream product recovery and purification. The performance of the upstream process can be justified by low production cost, consumption of renewable, nonedible feedstocks that are locally available. Currently, the edible feedstocks are still used in the conventional fermentation process. This is not only affecting the customers in terms of the demand/supply value chain, but it is also directly contributing on the high sale price of the food products as well as the monomers for bioplastic synthesis. To minimize the problems earlier stated, using the renewable, nonedible feedstocks in the production of monomers for bioplastic is promising. In addition, the high process performance is required. Key factors to achieve high production performance include robust microorganisms and simple but effective processes. The robust microbes can be found in nature or they can be metabolically engineered to the desired purposes. Terrilactibacillus laevilacticus SK5-6, a novel D-lactate producing bacterium was used in this work. The wild type T. laevilacticus SK5-6 was adapted in the preculture medium with the low concentration of yeast extract. From the experimental results, T. laevilactibacillus SK5-6 was adapted in the medium containing the very low yeast extract concentration of 0.45 g/L (97% reduction from the base case medium). The viable fermentation platform was developed in the 5 L stirred fermentor. The seed train was successfully developed for further fermentation scale up in the 30 L stirred fermentor. The obtained fermentation kinetics from the stirred fermentors (both 5 L and 30 L) were comparable to the theoretical values. The simplified economic evaluation was conducted. It was found that the raw material costs in D-lactic acid fermentation by the wild type strain (SK5-6) and the adapted strain (SK5-6T20) were low in comparable to the sale price of D-lactic acid in the market. From the findings previously mentioned, this indicates that the developing platform in this study is promising.