Growth optimization of Lactobacillus rhamnosus FTDC 8313 and the production of putative dermal bioactives in the presence of manganese and magnesium ions

Aims The study aimed to optimize the growth and evaluate the production of putative dermal bioactives from Lactobacillus rhamnosus FTDC 8313 using response surface methodology, in the presence of divalent metal ions, namely manganese and magnesium. Methods and Results A central composite design matrix (alpha value of +/- 1.414) was generated with two independent factors, namely manganese sulphate (MnSO4) and magnesium sulphate (MgSO4). The second-order regression model indicated that the quadratic model was significant (P < 0.01), suggesting that the model accurately represented the data in the experimental region. Three-dimensional response surfaces predicted an optimum point with maximum growth of 10.59 log10 CFU ml-1. The combination that produced the optimum point was 0.80 mg ml-1 MnSO4 and 1.09 mg ml-1 MgSO4. A validation experiment was performed, and data obtained showed a deviation of 0.30% from the predicted value, ascertaining the predictions and the reliability of the regression model used. Effects of divalent metal ions on the production of putative dermal bioactives, namely hyaluronic acid, diacetyl, peptidoglycan, lipoteichoic acid and organic acids in the region of optimized growth, were evaluated using 3D response surfaces generated. Evaluation based on the individual and interaction effects showed that both manganese and magnesium played an important role in the production of these putative bioactives. Conclusions Optimum growth of Lact. rhamnosus FTDC 8313 in reconstituted skimmed milk was achieved at 10.59 log10 CFU ml-1 in the presence of MnSO4 (0.80 mg ml-1) and MgSO4 (1.09 mg ml-1). Production of putative dermal bioactive and inhibitory compounds including hyaluronic acid, diacetyl, peptidoglycan, lipoteichoic acid and organic acids at the regions of optimized growth showed potential dermal applications. Significant and Impact of the Study This research can serve as a fundamental study to further evaluate the potential of Lactobacillus strains in non-gut-related roles such as dermal applications.