Study On Degradate Of Formaldehyde By Immobilized Methylobacterium Sp. Xjlw In A Reactor And Eliminating Of Formic Acid Accumulation

As a native toxin, formaldehyde is seriously harm to humans because of its widely used.Therefore, researches on how to eliminate indoor formaldehyde pollution catch more focus, especially the biodegradation method with its powerful application prospect.This study focus on the optimum formaldehyde degradation conditions of immobilized Methylobacterium sp. XJLW in the shaker and the formaldehyde bidegradation reactor. Meanwhile, a recombinant plasmid pMAL-c2X-fdh was constructed for solving the problem of formate accumulation during formaldehyde degradation.Sodium alginate was utilized to immobilize Methylobacterium sp. XJLW, which could resued in21batchs (12h per batch) without rupture to degradate formaldehyde (initial content5g/L) in phosphate-free MSM (adding10g/L CaCO3), when the cell concentration was5g/L.A thre phase fluid bed reactor was developed to evaluate the formaldehyde-biodegrading ability of immobilized Methylobacterium sp. XJLW. In the reactor, under repeated-batch degradation conditions (0.3L min-1aeration rate,75:300bead-to-liquid ratio,2g L-1cell concentration,30℃, and24h per batch), the immobilized cells stably degraded formaldehyde (5g L-1initial concentration) and the gels could be reused in20batches without rupture.The fdh fragment was cloned from the genome DNA of Yarrowia lipolytica and successfully inserted into the clonig vector of pMD19-T to form pMD19-fdh. After verification via colony PCR, sequencing and Blast, the fdh fragment in vector was99%identity to the target gene. Then a recombinant expression vector-pMAL-c2X-fdh was successfully constructed and transformmed in E. coli DH5a. The FDH was expressed in the recombinant E. coli. These results laid the research foundation for solving the problem of formate accumulation when formaldehyde was degradated by Methylobacterium sp. XJLW.