Effect of Aspergillus brasiliensis and Sphingobacterium spiritovorum interaction on the kinetic removal of benzo (a) pyrene in wastewater

Wastewater from the petrochemical industry commonly contains xenobiotic highmolecular-weight polycyclic aromatic hydrocarbons (HMW-PAHs). Prior to utilising the resources for human use, it is crucial to eliminate the pollutants in the aquatic environment, considering their potential risks to human health. Several bioremediation studies have been implemented. However, the investigation of the interaction between bacteria and fungi has been relatively limited. A. brasiliensis and S. spiritovorum were used to evaluate the potential interaction to degrade benzo(a)pyrene in wastewater as in monoculture and co-culture systems. The study begins with optimization of initial pH and temperature by Design-Expert software. The kinetic response of monoculture and co-culture (simultaneous and sequence) was evaluated with an in-depth analysis of the co-culture. This includes analysing the interaction type, surface hydrophobicity and adhesion prediction by using The Lotka-Volterra model, contact angle measurement (CAM) and thermodynamic DLVO theory respectively. A mathematical modelling study was conducted to analyse the growth kinetics of monoculture and co-culture while degrading BaP. The Design Expert examination indicated that A. brasiliensis thrives at a pH of 5.5 and a temperature of 40 ℃, while S. spiritovorum performs best at a pH of 7.6 and a temperature of 25 ℃. While co-culture is best at an initial pH of 6.0 and a temperature of 25 ℃. The efficacy of Design-Expert in optimising BaP degradation was confirmed using ANOVA analysis. Significantly, sequential treatment surpassed simultaneous, and monoculture treatment, exhibiting greater and faster removal of BaP of 79 % at 10 mg/L and more than 50 % for other concentrations. The study demonstrated the dominance of A. brasiliensis in the microbial community, its role in BaP degradation, and its symbiotic connections with S. spiritovorum. By altering the physicochemical properties, the degradation of BaP in co-culture was increased. The study of adhesion dynamics provided a clear understanding of the complex interaction between microorganisms, highlighting the significant influence of surface hydrophobicity. The Monod model was accurately applied to the correlation between the specific growth rate and substrate concentration derived from the growth curves. The kinetic parameter of an inhibitory model proposed by Haldane was effectively determined using the experimental data. The fourth-order Runge-Kutta method was extensively enhanced to compute the optimal parameter for a given non-linear problem. These findings provide insights into the interactions between A. brasiliensis and S. spiritovorum, highlighting their physicochemical characteristics and the breakdown of BaP. The mathematical modelling derived from these interactions can guide the development of more efficient bioremediation strategies for polluted environments, improving the degradation of contaminants in wastewater and soil treatment systems.