Study On Co-culture Of Methane-oxidizing Bacteria And Photosynthetic Bacteria To Produce Single-cell Protein

Single-cell protein is also called microbial protein or bacterial protein,which has rich nutritional value.Methane-oxidizing bacteria(methanotrophs)can use methane as the only carbon source and energy source to grow and produce single-cell proteins.Photosynthetic bacteria are harmless to humans and animals and are rich in protein.Photo synthetic bacteria and methane-oxidizing bacteria can exchange their metabolismgas and promote the growth for each other.In this thesis,the advantages of co-culture of methane-oxidizing bacteria and photo synthetic bacteria was studied.The conversion of metabolic gas between the two kinds of bacteria and the facilitation for the production of single-cell proteins was focused.The research include fellowing contents.In the first part of this thesis,whether the co-culture of me thane-oxidizing bacteria and photo synthetic bacteria can promote the growth of each other was explored.By using MATLAB software for data analysis,it has been found that the substances inside and outside the cells of methane-oxidizing bacteria and photosynthetic bacteria could promote the growth for each other,especially for the substances inside the cells.In the second part,the gas exchange between the mixed bacteria was studied by extending the air exchange interval.It has been found that the highest single cell protein yield could be obtained when the the air exchange interval was 24 h.However,with the prolongation of the substrate air replenish interval,the yield of the final single-cell protein was decreased gradually.However,the single-cell protein yield underlight illumination and CO2 replenish were higher than that of withoutlight illumination and CO2 replenish,indicating that photosynthetic bacteria could consume CO2 generated by methane-oxidizing bacteria and convert it into biomass.In the last part of the thesis,based on the optimal air change interval,the effect of gas proportion and light intensity on the mixed bacteria growth was discussed.The optimal growth conditions were obtained as that the light intensity was 20 ?mol/(m2·s-1),and the gas proportion of CH4 and O2 and CO2 was 4:4:2(V/V),the lag phase was 16.83 h,the maximum specific growth rate was 0.0031 h-1,and the dry weight of the single cell protein per 100 mL of fermentation broth was 0.149 g.Metal ions(Fe2+/Fe3+?Cu2+?Mg2+)were added to increase the yield of single-cell protein.It has been found that Fe3+ had the strongest effect butfew amount of M g2+ had a great influence on the yield of single-cell protein.