The Study Of Organic Acids Production From Rice Straw With Fermentation

China has abundant rice straw resource with the productivity of about 760 million tons per year,but the rate of resource utilization efficiency is low.To seeking out and developing the straw energy power by generating organic acids is become a research hotspots.Straw is mainly composed of macromolecules such as cellulose,hemicellulose,and lignin,it needs synergism of various microorganisms during biodegradation of straw.Compound strains is identified as a key to realize the rice straw resource utilization.In this study,we aim at searching highly efficient degradation of rice straw for generating organic acids,and the relationship between the dynamic degradation process of compound strains and fermented product in rice straw.Separation and identification the single bacterium from compound strains,mainly to research the fermentation characteristics,so enhance the compound strains of rice straw fermentation ability to produce organic acid,and reveals the ecological regulation mechanism of compound strains fermentation to produce small molecule organic acids.The main results were as follows:(1)The straw pretreatment soaking by 1% Na OH for 24 h,can effectively improve the adhesion of micro-organism and the biodegradation rate;SEM,FT-IR results show that the alkali pretreatment can dissolve wax layer on the surface of the rice straw and destroy the internal structure;Content of cellulose and hemicellulose incr eased by 17.6% and 12.7% respectively,effectively improve the biodegradation rate of rice straw.(2)Using the cow manure,cotton field soil,straw and biogas slurry as a fermentation inoculum;After enrichment culture,regard the speed of filter paper degradation as a evaluation index,selected three kinds of compound strains(YF,NJF,Y-NJF)with high cellulose-degradation ability;Qualitative screening and identification the main advantage single strain from compound strains through the CMC-Na and CZM plat,Blast homology analysis results show that N-2,N-11 and Y-1 are Bacteroides;N-8 and Y-3 are Colibacter;N-10,Y-7 and Y-10 are Xanthomonas.(3)It had a different effect between the three kinds of compound strains for the degradation of straw,NJF degradation effect of straw is the best,after 15 d the degradation rate reached to 80.5%,YF and Y-NJF were 36.4%,32.5% respectively.In the fermentation process of NJF,formic acid as the main product and yield of 2.40 g/L;YF is priority to generating propionic acid and yield of 0.78 g/L;Y-NJF is priority to producing acetic acid and yield of 1.86 g/L.In addition,the growth of three kinds of compound strains growth had a similar dynamic change,were shown as "the early rose-the mid and late dropped slowly – the last fell rapidly" changes in the situation,and maintained cellulose enzyme activity,NJF showed excellent endo-beta glucanase activity and beta-glucosidase activity,up to 3.03 U/ml and 3.27 U/ml;Y-NJF showed a good exo-beta glucanase activity,up to 3.07 U/ml;YF showed a well exo-beta glucanase activity,the peak value was 1.24 U/ml.(4)N(2,8,10,11,12)screening from NJF and Y(1,3,6,7,10)screening from YNJF,the single substrate(rice straw,glucose,lignin,cotton wool)of the 10 advantage single bacteria performed an acid fermentation experiments.The results show that the single bacterium had a similar regularity of degradation the substrate,the substrate degradation rate is: absorbent cotton > rice straw > lignin.But rice straw as the substrate,the organic acid production was significantly lower than the compound strains;while found that when using lignin as substrates the Y-7 had a outstanding performance,5d formic acid yield up to 0.39 g/L,was 1.18 times than compound strains Y-NJF;when using glucose as the substrate N-12 had a outstanding performance,5 d acetic acid production up to 0.71 g/L,was 1.18 times than compound strains;And optimized through the experiment,N(2,8,10)screening from NJF and Y(3?6?7)screening from Y-NJF produced acid amount relatively higher.(5)Add single bacteria in different fermentation stages,to strengthening the compound strains' ability to produced acid,the results showed that the reinforce effect: group B(2 d)group C > group A(1 d)>(3 d).Aggrandized compound strains produce acid results showed that the organic acid production from high to low were: formic acid > lactic acid > acetic acid > propionic acid > butyric acid.Y-6 in group B(2 d)had the best reinforce effect to compound strains for producing lactic acid,the yield increased by 0.12 g/L,Y-7 in group A(1 d)had the best reinforce effect to compound strains for producing formic acid,strengthen the yield increased by 0.44 g/L,Y-7 in group B(2 d)for had the best reinforce effect to compound strains for producing acetic acid,strengthen the yield increased by 0.13 g/L..(6)Researching the dynamic change regularity of reinforcement effect by Y-3?Y-7?N-2 and N-10 to compound strains as added in 2d.It showed that each single strain aggrandized compound strains to producing acetic acid performance the same dynamic change regularity.Tend to increase firstly and fall lately.The straw degradation effect of compound strain added Y-3 up to the best reinforcement on 4d,acetic acid yield increased by 0.28 g/L.While compound strain added Y-3 and Y-7 to producing formic acid,the degradation of straw inhibited at first and promoted lately.Compound strain added N-2 up to the best reinforcement on 6d,formic acid yield increased by 0.28 g/L,when added Y-7 it showed the best strengthening effect on 5d,formic acid yield increased by 0.30 g/L.The results indicated that in the case of the compound strain without any exogenous microbes,just reinforced the ecological regulation effect of the single bacterium that can effectively improve the straw degradation rate and the organic acids production,it provided a reliable theoretical basis and laid a foundation for further exploring in optimization for the straw fermentation process.