Induction and efficacy of immobilized laccase from Bacillus lichniformis for removal of phenolics in aqueous solution

Abstract

were approximately 0.015 day −1 and 85%, respectively, observed in microcosms containing microbial inocula (mass ratio of soil to inocula = 50:1), nutrient, and bulking agent addition (volume ratio of soil to bulking agent = 10–1) during 155 days of incubation. The TPH decay rate and removal ratio were only 0.0069 day−1 and 45%, respectively, in microcosms under intrinsic conditions. TPH decay rate could be further enhanced to 0.0196 day −1 in microcosms with frequent soil shaking and air replacement. Results also indicate that a decay rate of 0.0142 day −1 can be obtained in microcosms with the addition of chicken manures. Thus, chicken manures have the potential to be used as substitutes of commercial microbial inocula. Results show that TPH removal trend leveled off after approximately 74–93 days of operation. This might be due to the effects that the remaining compounds or byproducts might be less biodegradable, which caused the decreased TPH removal efficiency. The decreased oxygen and increased carbon dioxide contents in the headspace of microcosms indicate the occurrence of aerobic biodegradation. Moreover, the increased total heterotrophs in the early stage and increased total anaerobes in the later stage of the microcosm study also confirmed the shift of aerobic biodegradation to anaerobic biodegradation pattern when complete oxygen consumption was observed after 23 days of operation. Results will be useful in designing an ex situ soil bioremediation systems (e.g., biopile, landfarming) for practical application.