Methanotrophs Used In Fruit And Vegetable Preservation

Methanotrophs are a group of microbes with methane as the sole carbon and energ y source, which widely exist in nature. Methane Monooxygenase (MMO) is the vital e nzyme system in the metabolic process of methanotrophs. Under the action of molecula r dioxygen, It can catalyze methane into methanol. MMO can also catalyze another rea ction--olefin epoxidation reaction. In this reaction, ethylene can be catalyzed into oxir ane. Fruits and vegetables can release ethylene in storage process, which making the re spiratory intensity of fruit improve and improving the permeability of fruit tissue protop lasm to oxygen, and promoting the fruit respiration and other biochemical processes wit h oxygen. The activity of the enzymes in the fruit can be enhanced and the direction can be changed, which greatly reduce the fruit shelf life. For the traditional physical a nd chemical ethylene scavenger, In this thesis, the research content mainly includes thel ncrease of the MMO catalyzed ethylene epoxidation activity in methanotrophs, The cat alysts preparation of immobilized cell and thecomparison With the traditional ethylene s cavenger.In this thesis, the ability of MMO catalyzed ethylene epoxyoxidative into oxirane i n methanotrophs was improved by changing the culture conditions. It can be applied to the preservation of fruits and vegetables. Adding vitamin B12can increase the Genera tion amount of MMO. The concentration of8mg/L has The optimum effect. Exogenous electron donor formate can improve MMO of ethylene catalyzed epoxy vitality and pr ovide the NADH and make the reaction continued for the epoxidation. When the conce ntration is20mmol/L, the effect is Optimum. In the study of phosphate, we found it c an improve the permeability of methanotrophs cells, Which increasing the exposure of MMO and ethylene, the reaction rate can be improved. The optimal concentration is10mmol/L. When the three kinds of substances are in the optimum concentration of MM O catalytic ethylene epoxidation reaction, MMO may have the highest activity in epoxi dation.Methanotrophic cells can be immobilized to a specific carrier, forming immobiliz ed cell catalyst. Activated carbon with higher adsorption capacity proved superior to ot her carriers. The optimum addition of Adsorption carrier is10g/100ml bacteria Solutio n. In order to prevent the long time adsorption, causing MMO inactivation. the immobi lized methanotrophs which just reach the adsorption equilibrium is removed. After steril e washing, the immobilized cell catalyst can be obtained by secondary cultivating. The adsorption capacity can reach8.75mg cell/g, remaining67%of ethylene epoxidation catalytic activity. It also has adsorption ability for ethylene, which making the ethylene surrounding immobilized methanotroph reach a high concentration and starting the epoxi dation reaction. Thus can be used to remove the released ethylene by fruits and vegeta bles during storage.In compared with the traditional physical and chemical adsorbent, we find that ther e is no significant difference in the ability of ethylene scavenging. Ethylene scavengin g rate is a little slower than that of Potassium Permanganate ethylene scavenger at the beginning. Certain concentration is needed to start the reaction. But compared with the traditional physical and chemical ethylene scavenger, methanotrophic:ethylene scavenge r has its obvious advantages in the repeated use, no harmful material residues and low cost.