固定化Lysinibacilluscresolivorans的PVA-SA-PHB-AC复合载体制备及间甲酚的降解

针对生物降解过程容易受到外界不利环境影响及低浓度下动力学效率不高的问题,制备了具有吸附功能的微生物固定化载体并研究了对间甲酚的降解.在聚乙烯醇(polyvinyl alcohol,PVA)固定化载体中加入海藻酸钠(sodium alginate,SA)、聚羟基丁酸酯(poly-3-hydroxybutyrate,PHB)和粉末活性炭(activated carbon,AC),采用循环冷冻-解冻结合硼酸法制备了具吸附功能的PVA-SA-PHB-AC复合载体,并用其包埋固定化1株间甲酚优势降解菌Lysinibacillus cresolivorans,考察了载体微观结构、稳定性及扩散性对固定化微生物降解间甲酚的影响.结果表明,PVA-SA-PHB-AC载体比表面积和平均孔径分别为15.30m2.g-1和33.68 nm,对间甲酚的吸附容量和扩散系数分别为3.86 mg.g-1和5.62×10-8m2.min-1,可稳定使用60 d以上;固定化L.cresolivorans的间甲酚去除为吸附-降解的耦合,去除速率由载体传质速率与微生物降解速率共同决定,间甲酚浓度低于350 mg.L-1时,载体传质速率小于微生物降解速率,间甲酚去除速率由传质速率决定,浓度高于380 mg.L-1时相反;添加了吸附剂的载体扩散系数会减小,但能耐受更高的底物浓度,且在更宽的浓度范围可以实现高效的降解作用.间甲酚的降解规律及其差异性显示出经吸附功能改性的载体因传质作用的加强而实现反应动力学的提高,并且存在一个合理的浓度区间.

Preparation of PVA-SA-PHB-AC Composite Carrier and m-Cresol Biodegradation by Immobilized Lysinibacillus cresolivorans

Due to the effects of outer environment and concentration limit on the biodegradation of m-cresol, a carrier with adsorption ability was synthesized. A PVA-SA-PHB-AC composite membrane was prepared by adding SA, PHB and AC into PVA immobilization carrier using the combination of freezing-thawing and boric acid methods. A highly-effective m-cresol-degrading strain Lysinibacillus cresolivorans was entrapped in it and the effects of structural properties such as micro-structure, stability and diffusion coefficient on m-cresol biodegradation were investigated. The results showed that PVA-SA-PHB-AC composite membrane had uniform pore opening, of which the average pore size, specific surface area, m-cresol adsorption capacity and diffusion coefficient was 33.68 nm, 15.30 m²·g^-1, 3.86 mg·g^-1 and 5.62×10^-8 m²·min^-1, respectively. It could be reused for more than two months. m-Cresol removal by immobilized L. cresolivorans was the coupling of adsorption and biodegradation, and the removal rate was jointly determined by mass-transfer rate and biodegradation rate. When the initial concentration of m-cresol was lower than 350 mg·L^-1, the mass-transfer rate of PVA-SA-PHB-AC was smaller than the biodegradation rate. The m-cresol removal rate depended on the mass-transfer rate, when the concentration was higher than 380 mg·L^-1, it was determined by the biodegradation rate. The addition of adsorbent could decrease the mass transfer coefficient in the carrier, while the higher concentration of substrate could be tolerated and the efficient biodegradation could be achieved in a wider range of concentrations. The biodegradation of m-cresol by immobilized microorganism showed that the modified carrier increased the reaction kinetics in a range of initial concentrations.