Modeling and simulation of colonization of water-based metalworking fluid by Mycobacterium immunogenum

Abstract

The water-borne human pathogen Mycobacterium immunogenum (MI) originating from industrial wastewater contaminated with metalworking fluid (MWF), may pose serious public health risks. This warrants a front-of-the-pipe approach so as to control its growth in these fluids; this requires an understanding of its initial colonization process in pristine MWF. In this direction, using a synthetic MWF formulation, quadratic modeling of colonization was performed using response surface methodology (RSM) to understand parameter effects and interactions followed by in-silico simulation of optimal and inhibitory growth conditions using Genetic Algorithm (GA), and experimental validation. The experimental parameters that supported optimal growth of MI in culture included an alkaline pH (9.4) coupled with ambient temperature (30 °C), starter nutrient (OADC 2.028% v/v) and tramp oil (0.4% v/v.) Though OADC seemed to play an important role, tramp oil was found to be crucial for the colonization process. However, combinations of higher pH and lower temperature (∼23 °C) and lower pH and high temperature (∼37 °C) completely arrested the growth even in the presence of OADC and tramp oil. Collectively, the results provide critical information needed for achieving simulated laboratory culture of this pathogen for further research; this may facilitate development of novel biocide-independent strategies to effectively control this pathogen and its disposal-related hazards in aqueous streams.