Selection Of Potential Probiotics That Produce Catechol Siderophore And Dietary Enzymes From Human Faces

Catechol siderophores are small molecules with a high affinity for ferric iron,assembled by nonribosomal peptide synthetases?NRPS?.Catechol siderophores are widespread in human gastrointestinal tract?GIT?,and play an important role in keeping imbalance of iron nutrition in microorganisms.The dietary enzymes screted into extracelluar by human GIT microbiota,can play probiotic role in the nutrition and health of GIT during metabolism.Thus,screening of potential probiotics that produce catechol siderophore and dietary enzymes have huge potential value in the fields of food,medicine,agriculture and industry.In this study,we aimed to clone the fragment of NRPS A domain from 21 strains which are isolated from human faces,and 8 representative isolates were observed.Based on the phylogenetic diversity analysis of 16S rRNA and the animo acid of NRPS A domain,they are named Escherichia coli Gut 01?Bacillus sp.Gut 03?Escherichia coli Gut 07?Escherichia coli Gut 12?Escherichia coli Gut 13?Bacillus sp.Gut 14?Bacillu cereus Gut 16 and Escherichia coli Gut 20.The secondary metabolites of NRPS are classified into two groups,which are enterobactin?6 of 8?and bacillibactin?2 of 8?.The production of catechol siderophore exits significantly difference among 8 isolates based on the Rioux's test.B.cereus Gut 16 had the strongest ability to yield bacillibactin?94.75±0.40?M?,and E.coli Gut 07 for the enterobactin?66.48±0.10?M?.Four isolates that high yield of catechol siderophore were selected to analysis the activity of dietary enzyme.Four strains were all found to produce amylase,cellulose and?-glucosidase.All the other three isolates had lactase and phytase activity except B.cereus Gut 16.B.cereus Gut 16and E.coli Gut 20 produced lipase.And only B.cereus Gut 16 produced protease.The survive percentage during continue incubation in the simulated GIT condition in vitro,indicated that all the four strains had the ability to tolerance stomach acid and bile salt.After 6 hours,they all remain bigger than 60%in artificial gastric juice,and 102.84%¹14.70%compared to the initial after incubation 24 hours in artificial intestinal juice.Studies on the ability of adhesion and colonization of four strains showed that they had strong ability to adhesion and colonization on the surface of GIT,the autoaggregation after 20 h were between 30%⁴0%,the mucin binding rates were found between 26.20%⁵6.67%,and the percent of hydrophobicity to xylene,chloroform and ethyl acetate were between 5.72%⁵7.68%,31.65%⁴6.78%and 21.79%⁵5.18%,separately.Antibiotic susceptibilities of four strains showed that E.coli Gut 07?E.coli Gut 12 and E.coli Gut 20 were resistance against penicillin,benzyl isoxazole penicillin,tetracycline,doxycycline and erythromycin,while sensitive to the remains of 15 antibiotic drugs.B.cereus Gut 16 was resistance against carbenicillin,amikacin,tetracycline and erythromycin,while susceptibility to the others.Acute toxicity were studied in ICR mice,the oral LD₅₀ and MTD were more than 9.0×10¹² CFU/?kg bw?for four stains.All the mice had no treatment related diarrhoea,toxicity and death,and showed no significant differenc in organ index or histological changes.The four strains can be as potential probiotics for the next reaserch in application.The human GIT microbiota has been an important source to discover novel natural products and potential probiotics,because it harbors huge microorganisms and enormous gene.The four strains isolated from human faces with high production of catechol siderophore and several activities of dietary enzymes,can be considered as potential probiotics.The research validated that they were valuable for the application in food medicine,argriculture and industry,and the research on the nutrition and healthy of GIT.