Study On The Conditions And Process Enhancement Of Formaldehyde Degradation By Methylobacterium Sp.XJLW

Formaldehyde has very heavy toxicity on the organism. Biological degradation of formaldehyde will be one of the effective way for the removal of formaldehyde. The aim of this research was to optimize the conditions of formaldehyde degradation. And we added glucose and folic acid to accelerate the growth. The way of key enzyme gene knockout was to enhance the formaldehyde metabolic pathways.One new bacterial strain Methylobacterium sp. XJLW was isolated from soil by our laboratory. After a period of domestication, the concentration of formaldehyde-tolerant was up to1.2g/L. After single factor tests, the optimal conditions formaldehyde degradation were determined as yeast extract1g/L, KH2PO40.7g/L, K2HPO40.8g/L, MgSO40.5g/L, trace elements solution200μL/L, temperature30℃, pH7.0, amount by bacteria40mL/L. We study the effect of formaldehyde degradation with different initial inoculation. Under the optimal conditions with the DCW was0.02g/L,94%,39%,1%of0.6,0.9,1.2g/L formaldehyde were degraded in52h. Methylobacterium sp. XJLW resting cells(DCW was0.5g/L) can degradate2,15,30,45,60g/L formaldehyde. The formaldehyde degradation rates were100%,96.8%,84%,26.5%, and22.5%in8h, respectively. In order to investigate the transformation process of methanol, formaldehyde and formic acid, we study the15g/L formaldehyde degradation process by0.5g/L XJLW with CaCO3. In0-24h the data of formaldehyde concentration was droped rapidly from the initial15.7g/L to0.4g/L, while formic acid concentration was from0g/L increased to11.9g/L. Methanol concentration first increased but then decreased. In4h the methanol concentration reached10.1g/L, but in24h decreased to5.2g/L. In24h formic acid concentration was11.9g/L. After24h the formaldehyde and methanol degradation rate was slowly, but formic acid accumulate gradually.In order to enhance the formaldehyde degradation process, we add glucose and folic acid in the culture. Result revealed that the growth rate was accelerated apparently. We added methanol in the medium to research the growth situation in the different initial concentration of methanol as sole carbon source. Then we found that increasing the methanol concentration can not promote the growth rate of bacteria. The optimal concentration of methanol was1%. We added glucose and folic acid separately in the medium that with1%methanol as the sole carbon source. The OD600values of strain suspension were4.8and4.3, while the control was3.4. The conclusion was glucose or folic acid can promote to the growth of the bacteria.According to the Methylobacterium radiotolerans JCM2831strains gene sequence published in NCBI, a pair of specific primer was designed to amplify formaldehyde activating enzyme (Fae) gene fragment. The result showed that Fae gene obtained from Methylobacterium sp. XJLW was512bp in size, and has high homology with the key enzyme genes form Methylobacterium radiotolerans JCM2831and Methylobacterium populi BJ001. Then we introduced the Fae gene fragment into the vector pUC-18. On the basis of the results from PCR and restriction enzyme digestion, the recombinant vector pUC-18-Fae has been constructed successfully.