Mathematical modeling and optimization by the application of full factorial design and response surface methodology approach for decolourization of dyes by a newly isolated Photobacterium ganghwense

Abstract Dyes are chemicals found in industrial water discharge, which may harm aquatic life and humans. In this study, halophilic bacteria was isolated from sea water in Jeddah, KSA, and then identified using 16SrDNA sequencing technique. Mathematical modeling has been achieved to predict the number of runs needed to reach the maximum of dye removal. Then the effect of four independent variables (NaCl concentration, Peptone concentration, temperature and agitation) was studied using full Factorial Design (FFD) for the determination of optimal abiotic and biotic condition, which reaches a maximum percentage of colour removal (% of decolourization) in artificial seawater (ASW). A model was proposed for the statistical analysis of colour removal prediction. Analytical techniques (UV–vis and FTIR) was also used to determining the degradation mechanisms. The active strain was then genetically characterized to identify genes related to chemical and dyes biodegradation. The isolated strain was identified as Photobacterium ganghwense. Our results revealed that P. ganghwense (5.106 CFU/ mL) was able to decolourize four tested dyes (Methyl orange, Congo red, Crystal violet and Malachite green) in modified ASW with different degrees and the maximum of decolourization was attributed to malachite green (79.61%). The biodegradation capability of the selected strain was confirmed by UV–Vis spectrum and FTIR analysis. Experimental data and model predictions were found to be in good agreement. Genomic analysis confirm the presence of several enzymes (reductase, dehydrogenase, oxidase, kinase, hydrolase, and transferase) associated with dyes and xenobiotic degradation, indicating its possible use in biotechnology applications.