Study On The Screening Of Kelp Degrading Bacteria And The Composition Analysis Of Fermentation Products And The Application In Plant Growth

With the continuous development of marine active substances research,people pay more and more attention to brown seaweed polysaccharides.Not only does natural alginate have good biological activity,but also its degradation product,algae oligosaccharide,has strong biological activity,which has great development value and broad development prospects.This paper mainly studies the isolation and screening of kelp degrading bacteria,their degrading function to kelp,the composition analysis of kelp fermentation products,the effects of kelp fermentation broth on rape seed growth and developmentand soil microbial flora.(1)Isolation,Identification and Screening of Degrading Functional Bacteria from Laminaria japonicaIn this paper,fresh kelp was collected from a kelp farm in rongcheng,shandong province,and the relatively stable microflora with kelp degradation effect was obtained after multiple enrichment of the carried microflora.Thirty strains of bacteria were isolated and purified.16SrDNAsequencing and screening were carried out to select strains and strain combinations with good degradation effect.Strains containing pectinase and alginate lyase were selected by using selective medium,the sole carbon source of which is pectin or sodium alginate,and single or compound bacteria with better degradation effect were selected by measuring the alginate content in kelp fermentation broth and the degradation effect of corresponding single and compound bacteria.The results showed that the degradation effect of bacteria 1-2 and compound bacteria containing 1-2 and 3-10 was over 85%,among which the degradation effect of compound bacteria 1-2 and 3-10 was 95%,which was better.In addition,for the compound bacteria with poor effects,the others reached more than 70%,and the effect wasrelatively betterthan that of thesinglebacteria.(2)Detection ofkelp fermentation brothCrude extraction of algal oligosaccharides:The extraction of algal oligosaccharides from kelp fermentation broth was determined by 95%ethanol solution and the content of reducing sugar and total sugar in kelp fermentation broth was determined by 3,5-Dinitrosalicylic acid colorimetry.The results showed that the reducing sugar and total sugar content of the kelp fermentation broth fermented by 1-2 and 3-10 composite bacteria with 20%kelp before extraction were 8.76 g/ml and25.59g/ml respectively,and the results were the best.After crude extraction of trehalose oligosaccharides,there were almost no reducing sugar and total sugar in the three kinds of kelp fermentation broth,so trehalose oligosaccharidescouldbe extracted by theabovemethods.TLC:Through the analysis of developer and chromogenic agent,we can see that the striping effect is better when the developer is n-butanol:ethyl acetate:isopropanol:glacial acetic acid:water=2:6:6:4:1,and the chromogenic agent is 20%sulfuric acid-methanol.The bands of kelp fermentation broth were slightly lower near sucrose.It can be inferred that most of the algal oligosaccharides in the kelp fermentation broth are trisaccharides.(3)Effects of kelpfermentation broth on seed germination and growth of rapeseedBy diluting 50,100,500,1000,2000 times kelp diluent with water as the control,rapeseed seeds were treated,and the germination of rapeseed seeds and the growth of roots and stems after germination were observed.The experiment showed that the germination rate of rapeseed seeds diluted by 1000 times of kelp fermentation broth was the highest 94.5%,which was 58%higher than the control group.The best growth condition of brassica napus sprouts and roots was 4.44cm,which was 1.23cm higher than the control group.The best growth rate was 5.44cm,3.52cm higher than the control group.The seeds of rapeseed with good seedling were planted in a pot and watered with seaweed diluent diluted by water respectively.The experiment showed that the stem length of rapeseed seedlings irrigated with kelp fermentation broth diluted 2000 times was 7.90cm,2.54cm higher than thecontrol group,and longerthan theseeds ofother diluents.Based on the above results,kelp fermentation broth diluted by 2000 times had the best growth promoting effect on rape seeds,followedby thetreatment group diluted by 1000 times.(4)Effects of seaweed fermentation broth on soil microbialflora and plantgrowthThe seedlings of rapeseed were planted in a pot with sterile soil containing suspension of soil bacteria.Different kelp diluents were irrigated.The growth of rapeseed and soil microorganisms were observed with water as control.The results showed that rapeseed plants grew better at 1500 c and the plants were larger.The number of actinomycetes,bacteria and fungi in soil when they are diluted 1500 times by kelp fermentation broth is 2.34 x 10~7,5.7 x 10~6 and 3.14 x 10~7,respectively,whichshows that the dilution has a more obvious effect onthe growthof soil microorganisms.