Production Of Methane Protein And Nucleic Acid Removal

Methanotrophs are a group of gram-negative eubacteria that utilize methane as the sole energy and carbon source. Methane is a complete reduction carbon form that can be used for methane single cell protein (SCP) production. There is no direct toxicity, carcinogenic polycyclic aromatic hydrocarbons and other impurities in methane material. In fact there is no need of expensive purification equipments for methane single cell protein production. However, the production of methane single cell protein is still in the experimental stage. In this thesis, we mainly focuses on the influences of some growths on Methylosinus trichosporium3011growth in the fermentation processes, and the removal of excessive nucleic acids. Finally, a simple effective method for nucleic acid removal was established.Firstly, we found that M.trichosporium IMV3011could use methane and/or methanol as sole carbon source for cell growth in an open system. With the comparison between the open and close system for M.trichosporium IMV3011culture, a new open fermentation strategy, was developed for the production of SCP.Semi-continuous culture of M.trichosporium IMV3011was conducted under intermittent replacing culture medium per24h. This continuous culture method was employed to find the optimal stage for fresh medium supplementation.It has been found that the positive growth factors can be accumulated at the initial stages and the fresh culture medium would be supplemented after48h cultivation.The effects of folic acid, VB12, D-biotin, riboflavin on the growth of M.trichosporium IMV3011was studied. The results showed that the addition of folic acid, VB12, D-biotin, and riboflavin shortened the lag phase. While there was little effect of those growth factors on the maxmium growth rate. When the addition of D-biotin was lOug/L, the lag phase was shortened to5.8h, but the dry weight was only0.29g wtL-1which was lower than that no addition of D-biotin. As compared, when the addition of folic acid was5ug/L, the lag phase was shtortened to3.2h, the dry weight was0.97g wtL-1which was3times of that was no addition of folic acid. Also, when the addition of riboflavin was5ug/L, the lag phase was shortened to15.1h, the dry weigh was0.77g wtL-1which was2.5times of that was no addition of riboflavin. Futher more, when the addition of VB12was0.5ug/L, the lag phase was shortened to18.7h, the dry weight was0.84g wtL-1which was2.7times of that was no addition of VB12. In conclusion, this simple addition of growth factor increased the production amount of SCP and shortened the fermentation cycle.The research established a fundation for the commercial production of SCP by the Methylosinus trichosporium IMV3011. Ultrasonic method, concentrated salt method, cooperation method between ultrasonic and concentrated salt method, and cell autolysis method were studied to select an optimal nucleic acids removal method. We found the cell autolysis method is the optimal approach for nucleic acids removal according to the results. Also the effect of temperature, cell concentration, treatment time, and the pH value on the nucleic acid removal were studied.By the single factor and orthogonal experiments, the optimal experimental scheme was established, the optimum conditions for removal of excess nucleic acids in M.trichosporium IMV3011are as follows: temperature70℃, cell concentration of0.9%(wet weight), the processing time50min, the pH value of10. Under the optimal conditions the maximum amount of nucleic acid removal was44.75ug/ml. The removal rate was50.2%.