Exsitu assessment of potential free (FC) and immobilized cell (IC) bacteria used as engine oil (UEO) degraders in the degradation of UEO in liquid yeast extract minimal salt medium (YEMSM)

Abstract

Used engine oil (UEO) contains potentially toxic substances that harmful humans and the ecosystem. Its dangerous pollution requires customized, efficient adsorptive bioremediation. This study investigates the local soil bacteria that can remove petrol-UEO (shell 15–40) by metabolic capability in UEO-YEMSM, previously isolated from UEO-polluted soil in KL, Malaysia. The biosorptive bioremediation capabilities of the free cell (FC) formula for UEO have been studied using pure Ochrobacterium intermedium LMG 3301 and mixed culture consortia of Ochrobacterium intermedium LMG 3301 plus Bacillus paramycoides MCCC1A04098 (BC), with an inoculation size of 3 × 109 CFU/mL in 0.675% (v/v) UEO-YEMSM. To study the UEO adsorption bioremediation of IC systems and compare them to the same FC systems, pure and mixed bacteria cells were immobilized using alginate-attapulgite-calcium carbonate (AAC). On day 24, the IC systems exhibited the removal of nC9 to nC17 with a 30% increase in TPH obtained with O.intermedium and the 18% by O. intermedium + B. paramycoides (BC) in UEO, as compared to the same FC systems. The AAC-IC of O. intermedium and the BC also removed nC9-nC29 to 93% and 98%, demonstrating the adsorptive-biosorptive bioremediation capacity of IC-systems with efficient mass transfers of experimental effectiveness factor (η) values of 1.04, and1.05, close to FC system η = 1. The enhanced degradation and bacterial growth in the AAC-IC systems indicated the high potential of AAC beads to be applied in the insitu bioremediation of UEO-polluted soils/water environments in KL, Malaysia.