Isolation of a novel thermophilic bacterium capable of producing high-yield bioemulsifier and its kinetic modelling aspects along with proposed metabolic pathway.

Bioemulsifiers form stable emulsions and lower surface tension between two phases with potent anti-microbial activities. Some applications of bioemulsifier are performed at high temperatures and hence production of bioemulsifiers that are stable at high temperature is required. This study aimed at the production of bioemulsifier by an unexplored bacterial strain isolated from a local hot spring. The parameters tested for bioemulsifier production (emulsification ability, surface tension measurement and product formation) showed that 24 h is the optimal time for the production of bioemulsifier by strain S3 with yield of 1.4 g/l. The logistic growth curve of bacterial strain was analysed and kinetic constants for substrate utilisation and product formation were determined by Luedeking-Piret kinetic models. The bacterial strain S3 was Gram-positive and was classified as a strain of Brevibacillus borstelensis. The specific growth rate of the organism was 0.0096 h-1 with the kinetic rate constants as 11.246 (γ) and 10.626 (δ) for Luedeking-Piret substrate and 3.8423 (α) and - 1.9075 (β) for Luedeking-Piret product. Knowledge of these values will help in estimating the substrate utilisation or bioemulsifier formed at any time point. These studies will also help in understanding internal metabolic fluxes hence rigorous analysis of metabolic pathway of bioemulsan is also performed in this study. Graphical abstract.