石油および環境バイオテクノロジージャーナル

概要

Degradation of Elevated Concentrations of Phenol Using Two-Stage Immobilized Cell Reactor with Bacillus subtilis and Acinetobacter lwoffii

Bahobail AS

Two vertical rotating immobilized cell reactors (VRICRs), one with the Bacillus subtilis, BDCC-TUSA-3 for bisurfactant (surfactin) production and the other with Acinetobacter lwoffii, accession number KM985371 for phenol biodegradation were constructed, with polyurethane foams as the attachment support. They were separately optimized for surfactin production and degradation of phenol respectively. Then, the two reactors were combined to form a two-stage VRICR where an appropriate fraction of Bacillus sp. reactor effluent, containing surfactin (0.20 g.l-1, 0.25 g.l-1 or 0.30 g.l-1), was mixed with the influent fed into A. lwoffii reactor, containing various concentrations of phenol (1500 mg.l-1, 1870 mg.l-1 and 2250 mg.l-1). The VRICR was operated continuously over more than two weeks. Cell growth, cell viability, degradation efficiency of phenol and specific degradation rate (SDR) were followed over periods of operation. The best results were obtained when a steady state was reached with 45.6 g.l-1, 98%, 100% and 810 mg phenol. g immobilized cells-1.h-1 for cell growth, cell viability, degradation efficiency and SDR respectively. Additionally, surfactin was produced from reactor 1 at high concentration (5.05 g.l-1) with a volumetric reactor productivity of 757.5 mg surfactin l-1.h-1 which represents an extra added-value product that could markedly decrease operating costs. The efficient process for phenol degradation, with no secondary by-products, coupled with potential applicability of simultaneously produced surfactin that could be utilized in many industrial applications, makes the two-stage VRICR a potential candidate for a clean, cost-effective and environmentally sustainable process.