Growth and Extracellular Enzyme Activity Responses of a Multi-enzymic Strain of Serratia sp. in a Simulated Diesel-contaminated System

Abstract

Aim: The present study was aimed at elucidating the alternative metabolic preferences of Serratia sp. strain DW2 that permitted its survival in a diesel-contaminated environment. Study Design: We adopted a 4 x 4 x 3 completely randomized design of a full-factorial experiment for the study. Place and Duration of Study: The study was conducted at the Department of Microbiology, University of Calabar, Nigeria, during the months of March and June, 2019. Methodology: In this study, Serratia sp. strain DW2 was isolated from Douglas Creek water of the Qua Iboe Estuary, along the Qua Iboe terminal at Ibeno, Nigeria, as a significant biological contributor to the decontamination process through inherent ability to utilize diesel oil hydrocarbons. This paper elucidated the growth and responses of the bacterial lipase, caseinase and gelatinase activities to diesel-oil hydrocarbon contamination. Results: Range finding test results showed that the bacterium could grow in the presence of water soluble fraction of diesel (wsf-D) concentration between .0042 and .0335 µg/mL, albeit with increasing lag time and decreasing specific growth rate when compared with growth in glucose-Bushnell-Haas broth. Lag time changes were not significantly influenced by exposure time but changes in specific growth rate were. Gelatinase activity was most susceptible to toxicant onslaught but was least affected by exposure time. Conversely, lipase activity was the most affected by exposure time. Toxicant concentration/exposure time interaction of a two-way analysis of variance model for caseinase activity was not significant (P > .05) but those for lipase and gelatinase activities were. Conclusion: The bacterium survived diesel toxicity by exploiting its lipase and gelatinase activities for provision of alternative sources of carbon, energy and nitrogen to drive ecosystem decontamination in the event of refined petroleum contamination.