| QS is a phenomenon in which bacteria communicate with each other through signal molecules to regulate gene expression.The quorum-sensing signal molecule is the key substance that causes the quorum-sensing phenomenon of bacteria,and the main signal molecule of Gram-negative bacteria is N-acylhomoserine lactone(AHLs).As the bacteria grow,the bacterial density increases After the content of secreted AHLs reaches the threshold,quorum sensing occurs to regulate biofilm formation,cell differentiation,motility,extracellular polysaccharide formation,the induction of virulence factors of pathogenic bacteria,and the symbiosis of bacteria and eukaryotes.In this study,a quorum-sensing signal molecule secreting bacterium(Aeromonas hydrophila A-L2)was screened to study the secretion characteristics of the signal-producing molecule,and A-L2 was embedded into PVA/SA/Zn ONPs by live cell embedding The immobilized particles were added to the 100mg/L pyrene solution to further explore the enhancement effect of immobilized(QS)secreted bacteria on the biodegradation of pyrene.The specific research results are as follows:(1)A-L2 bacteria conform to the S-shaped growth curve,During the growth process,the AHLs content changes first and then stabilizes.The optimal AHLs secretion condition is 30?,p H=7,Na Cl content 10g/L,sugar source is glucose 5g/L,nitrogen source is tryptone peptone 10g/L.The secretion amount under the best secretion characteristics is 21.07?g/m L.(2)Take A-L2 bacteria and Pyrene degrading bacteria(Staphylococcus sciuri S-3)as the control group to explore the strengthening effect of QS on the degradation of pyrene by S-3 bacteria.Obtained mixed bacteria(1/2A-L2+1/2S-3)during the degradation process,the total amount of AHLs up to 22.32?g/m L,and catechol 1-2dioxygenase C120 and catechol The enzyme activity of 2-3 dioxygenase C230 reached1.35 U/mg,0.196 U/mg,the polysaccharide concentration was stable at 0.96 mg/L,the maximum protein concentration reached 2.70 mg/L,and the degradation rate reached67.67%.(3)Using PVA/SA+Zn ONPs as the immobilized carrier to embed A-L2 bacteria to make immobilized QS secreting bacteria,and explore the effect of immobilization on AHLs secretion after immobilization.Finally,when the added Zn ONPs is 0.3g/L,the mechanical strength of the immobilized particles reaches 98.670%,the mass transfer efficiency reaches 89.86%,and the specific surface area is 8.353 m~2/g.Under the conditions of the highest mass transfer efficiency and the guarantee of mechanical strength,the addition of Zn ONPs is selected.The content is 0.3g/L.Under the same conditions,the total amount of AHLs of immobilized(QS)secreting bacteria during growth can reach 48.27?g/m L,which is much larger than free bacteria.(4)Add PVA/SA/Zn ONPs immobilized QS secreting bacteria with the same amount of dry bacteria to the S-3 sacterial pyrene degradation system,and compare with mixed free bacteria and PVA/SA immobilized QS secreting bacteria to study PVA/SA.The characteristics of Zn ONPs living cell immobilized particles compared with free bacteria during pyrene degradation.As a result,the activity of AHLs of PVA/SA/Zn ONPs immobilized secretory bacteria was up to 52.34?g/m L;catechol 1-2dioxygenase C120 and catechol 2-3 dioxygenase C230 were active C120 The highest value is 3.12 U/mg,and the highest value of C230 can reach 0.38 U/mg,which is much larger than free bacteria;EPS results show that the maximum polysaccharide content of immobilized(QS)secreting bacteria when degraded to 84h reaches 2.98 mg/L,protein The highest concentration reached 8.94 mg/L;the highest degradation rate reached93.41%,both higher than free bacteria.(5)Reuse experiments on the PVA/SA/Zn ONPs immobilized secreted bacteria after use,and the degradation rate reached 99.98%at 48h when the number of repetitions was 18 times,and the pyrene degradation rate could still reach more than80%after 48 times,Indicating that the immobilized cells have a long service life and stable pyrene degradation ability. |
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