Optimization of fermentation conditions for PHA-producing strains

Abstract

Over the years, as more and more attention has been paid to environmental problems, the state has promulgated a number of plastic restriction orders, intensifying efforts to rectify the "white pollution" problem and promote "sustainable development". Under this background, among many degradable biomaterials, PHA, also known as polyhydroxyalkanoates, is considered to be a substitute for plastic products. The physical properties of PHA molecules are similar to those of common plastics, Monomer molecules with different lengths can be used to produce materials with different properties such as stretchability and hardness. Although PHA molecules can be produced by a variety of microorganisms through their internal metabolic pathways and the corresponding materials can be produced in the laboratory, there are still some problems in making them applicable to large-scale production and practice. In this study, the fermentation conditions of PHA were optimized by single factor screening experiment, using E. coli JM109 as the chassis engineering strain, using cheap recycled glycerol as carbon source, and using indoor shake flask culture method. Without considering the interaction of each component, it was found that the optimal fermentation temperature was 37 ℃, the yield was 3.45 G/L, the optimal fermentation time was 48 H, the yield was 3.32 G/L, the optimal pH value was 7.0, the higher yield was 3.82 G/L, and the optimal rotation speed was 200 rpm. The yield can reach 4.11 G/L. This study not only reveals the internal relationship between microbial growth and PHA synthesis in the fermentation process, but also provides a strong theoretical and practical basis for the industrial production of biodegradable plastics. This study deeply understood the key factors found in PHA fermentation production, which has guiding and reference significance for the further transformation of microbial strains, the optimization of fermentation process and the expansion of PHA application fields in the future, such as medical materials and packaging materials.