Isolation And Identification Of Photosynthetic Bacteria And Its Application

Using photosynthetic bacteria to remove various pollutants has become the focus of research on organic wastewater pollution because of its strong ability to degrade,low cost,good effect and no secondary pollution.At present,most of the bacteria are introduced from abroad,which induce the problems of instability,poor effect and other issues.Therefore,in order to improve the utilization of photosynthetic bacteria,it is necessary to screen out photosynthetic bacteria efficiently from the local.In this thesis,5 photosynthetic bacteria strains were isolated from the sewage of Risheng Food Co.,Ltd.and the entrance of Dianchi Wetland Park.They were also identified according to the morphology,cultural characteristics,cellular spectrum and 16S rRNA sequence.In this paper,the effects of the isolated photosynthetic bacteria on the metabolism of formaldehyde,benzene,as well as the purification of sugar cane molasses were studied.The main results are as follows:1.The 16S rRNA sequence of the strain showed that:the strain RX-1 had the closest genetic relationship with the Rhodobacter sphaeroides,and its sequence similarity was 92%,which should belong to the Rhodococcus in the phylogenetic relationship;The strain RX-2 had the closest genetic relationship with the Rhodopseudomonas palustris,and its sequence similarity was 100%,which should belong to the Rhodopseudomonas in the phylogenetic relationship;The strain DC-1 had the closest genetic relationship with the Rhodobacter capsulatus,and its sequence similarity was 98%,which should belong to the Rhodococcus in the phylogenetic relationship.The strain DC-2 had the closest genetic relationship with the Rhodopseudomonas palustris,and its sequence similarity was 98%,which should belong to the Rhodopseudomonas in the phylogenetic relationship;The strain DC-3 had the closest genetic relationship with the Rhodobacter capsulatus,and its sequence similarity was 97%,which should belong to the Rhodococcus in the phylogenetic relationship.By sequence alignment,The strain RX-2 and strain DC-2 were not the same species of Rhodopseud-omonas palustris,and strain DC-1 and strain DC-3 were not the same species of Rhodobacter capsulatus.Physiological and biochemical research showed that 5 strains of photosynthetic bacteria belong to a purple non-sulfur photosynthetic bacteria groups without oxygen production of photosynthetic bacterium,because these bacterium with gram negative bacteria do not produce oxygenduring the growth process of bacterium.The optimum temperature,the optimum pH value and the optimum inoculation amount of these bacterium were 30 0C,7 and 20%,respectively.2?The purification capacity of liquid formaldehyde for 5 strains of photosynthetic bacteria are different.The strains of RX-1 and DC-1 were able to purify 2 mM formaldehyde and tolerate 4 mM formaldehyde.The strains RX-2 and DC-2 could purify 2 mM and 4 mM formaldehyde respectively,but both tolerated 6 mM formaldehyde.DC-3 could purify 6 mM formaldehyde and tolerate 8 mM formaldehyde.Among the five photosynthetic bacteria,the strain DC-3 had the strongest ability to purify and tolerate formaldehyde.3?13C-NMR analysis of photosynthetic bacteria formaldehyde metabolites showed that RX-1 converts 4 mM formaldehyde to formic acid,glyoxylic acid,glucose?[U₁3C]Gluc?,light pyruvate?DHA?,fructose?[U-13C]?,alanine?Ala?and glutathione?GSH?,suggesting that the main metabolic pathways of RX-1 are linear pathways of glutathione-linked FaDH for foremaldehyde oxidation,ribulose monophosphate pathway and serine recycle pathway.RX-2 converts 4 mM formaldehyde to[2-13C]Ser,Ala and GSH,suggesting that the main metabolic pathway of RX-2 is a serine recycle pathway.DC-1 converts 4 mM formaldehyde to[U-13C]Fruc,DHA,[2-13C]Ser,[2-13C]Gly and malic acid?[2-13C]Mal?,suggesting that the main metabolic pathway of DC-1 are ribulose monophosphate pathway and serine Recycle pathway.DC-2 converts 4mM formaldehyde into[U-13C]Fruc,formic acid and GSH,suggesting that the main metabolic pathways of DC-2 are ribulose monophosphate pathway and linear pathways of glutathione-linked FaDH for foremaldehyde oxidation.DC-3 converts 4 mM formaldehyde to[U-13C]Glue,[U-13C]Fruc,[2-13C]Ser and Ala,suggesting that the main metabolic pathways of DC-3 are ribulose monophosphate pathway and serine recycle pathway.4?5 strains of photosynthetic bacteria had different effects on the purification and tolerance of benzene homologues.Under the condition ofthe inoculation amount of 20%,pH7 and 30?,RX-1 strain could purify completely 6 mM benzene,2 mM toluene and 4 mM xylene by 8d,6d and 8d,respectively,and tolerant 6 mM benzene,4 mM toluene and 4mM xylene respectively.The strain RX-2 was able to completely purify 6 mM benzene,2 mM toluene and 2 mM xylene by 8 d,7 d and 7 d,respectivey,and tolerat 8 mM benzene 4 mM toluene and 4 mM xylene,respectively.The strain DC-1 was able to completely purify 4 mM benzene,2 mM toluene and 2 mM xylene by 8 d.and tolerate 4 mM benzene,4 mM toluene and 2 mM xylene,respectively.The strain DC-2 was able to completely purify 6 mM benzene,4 mM toluene and 2 mM xylene by 6d,.8d and 7d respectively,and tolerate 12 mM benzene,6 mM tolueneand 4 mM xylene,respectively.The strain DC-3 was able to completely purify 2 mM benzene by 7 d,but could not purify toluene and xylene,and its tolerable concentrations of benzene,toluene and xylene were 4 mM.5?5 photosynthetic bacteria strains,Bacillus sp and mixed liquid with strain DC-1 and Bacillus sp treated with five different concentrations of sugarcane waste molasses.The results showed that 5 photosynthetic bacteria strains RX-1,RX-2,DC-1,DC-2 and DC-3 had the best effect on sugarcane waste molasses with 0.5%o concentration,being 77.81%,82.17%,91.19%,86.62%and 87.99%of COD removal rate,respectively,in which COD removal rate of DC-1 treatment reached the highest 91.19%.Bacillus COD removal rate reached 74.68%.The purification ability of the mixture of DC-1 and Bacillus sp.was the highest with 96.16%of the removal rate of COD.