Dr. Nuttha Thongchul
Institute of Biotechnology and Genetic Engineering, Chulalongkorn University, Thailand
Title: Low cost technology platform development for a bioplastic precursor
The growth of bioplastic industry currently suffers from the high production cost of its fermentative monomers. It is claimed that types of media contribute approximately 50% of the total operating cost. To minimize this problem, using the renewable, nonedible feedstocks in the production of monomers for bioplastic are promising. In addition, robust microorganisms and simple fermentation processes are key factors to achieve efficiently high production performance of bioplastic monomers. Terrilactibacillus laevilacticus SK5-6 was previously screened from the soil sample in Thailand and identified as the novel D-lactate producing bacterium. T. laevilacticus SK5-6 exhibited an excellent performance in producing an optically pure D-lactate (102.72 g/L final titer with 0.82 g/g glucose, 2.14 g/L×h productivity, and 99.63% enantiomer excess) in a shake flask cultivation. A high concentration of yeast extract of 15 g/L was used during the preculture step to generate cell biomass of T. laevilacticus SK5-6 while a sole glucose solution was used in the fermentation step for D-lactate production. To lower the consumption of yeast extract during the preculture step; thus, reducing the operating cost, phenotypic adaptation of T. laevilacticus SK5-6 was introduced in this work. The wild type T. laevilacticus SK5-6 was subsequently cultivated in the preculture medium with a lowered yeast extract concentration. From several passages until the 20th transfer (T20) of the growing culture in the preculture medium containing lowered yeast extract concentrations, phenotypic adaptation caused the adapted strain to grow under very limited yeast extract concentration of 0.45 g/L (97% reduction). The reduction of yeast extract in the medium could lower the production cost by approximately 30 baht per kilogram of D-lactate produced. Meanwhile, the fermentation platform for wild type strain of T. laevilacticus SK5-6 was also developed in the 5 L stirred fermentor to ease the operation in the pilot scale and industrial scale. The preculture seed train was formulated for producing the sufficiently high amount of T. laevilacticus SK5-6 with the suitable physiological stage for D-lactate production in the fermentation stage. The results indicated that the inoculum size from the stock culture slant as well as the preculture age in the seed flask did not affect the fermentation kinetics. However, the higher the amount of the preculture seed to be transferred to the fermentation step, the better fermentation performance was acquired. With this fermentation platform, a larger scale fermentation optimization was conducted in the 30 L stirred fermentor. The power input per unit volume (P/V) and the impeller tip speed (NiDi) was tested as the scale-up factors. In addition, the seed train was varied and developed for acquiring the similar growth and acid production patterns to those in the 5 L stirred fermentor previously optimized.
Dr. Nuttha Thongchul is Associate Professor of Institute of Biotechnology and Genetic Engineering and Adjunct Professor of Biotechnology Program at Chulalongkorn University, Thailand. She is also serving on as the committee members of technical experts in Biobased Industries under the Act Strategic Based Investment commissioned by Board of Investment (BOI) of Thailand. Dr. Thongchul received her B.Eng. degree in Chemical Engineering from Chulalongkorn University (Thailand), M.Eng. in Bioprocess Technology from Asian Institute of Technology (Thailand), and Ph.D. degree in Chemical Engineering from The Ohio State University (USA). Her research interest includes biotechnology, bioengineering, and bioprocessing with emphasis on novel fermentation and bioseparation process design as well as biobased industrial production platform development for production of value-added products. She is currently a member of American Institute of Chemical Engineers (AIChE) and serves on as the area chair in Food under Food, Pharmaceutical, and Bioengineering Division.