The Effect Of Lactic Acid Bacteria On The Fermentation Quality Of Rice Straw Silage

Silage is largely based on fermentation by lactic acid bacteria(LAB),which can be added deliberately as starter cultures or are adventitious microflora selected during the fermentation process.Their population dynamics and activity associated with biochemical processes are of crucial importance for the development of the quality of ensilage.The total straw output of the three major crops(rice,cotton and wheat)in China was 52,056 × 104t,of which the rice straw was 21,129 × 104t.The problem of efficient exploitation and cleaner utilization of crop straw has attracted significant attention around the world.Crop straws,which have high sugar content(such as corn)and forage grass are silage crops used widely for ruminant feed production in China.In this experiment,we chose wilted rice straw as the raw material.Most fresh rice straw was discarded in the field and becomes wilted before use.There are some disadvantages of wilted rice straw as the raw material for silage:(1)Rice straw is composed mainly of cellulose,hemicellulose and lignin,hence,it has low digestibility,(2)The nutritional content of dried rice straws is low,which results in low abundance of natural populations of lactic acid bacteria and(3)Rice straw has a hollow stem,leading to the possibility of mold growth during ensiling.Firstly,we should ascreen of lactic acid bacteria that are suit to rice straw silage and probe into the diversity of spoilage organisms that effect rice straw silage quality.The diversity of cultivable microorganisms between pre and post-ensiled straw were in vestigated and two strains of lactic acid bacteria from post-silage straw were isolated.According to morphological characteristics of bacterial colonies,bacterial strains subjected to amplified ribosomal DNA restriction analysis(ARDRA).Then combine the ARDRA and RAPD-PCR technology to separation and identification lactic acid bacteria from rice straw silage.By the dilution plate method,the number of aerobicbacterium from 7.60×107 cfu/g down to 2.43×106 cfu/g,fungi populations significantly decreased from 4.43 ×105 cfu/g to 86 cfu/g.However,the number of lactic acid bacteria increases from 4.16×105 cfu/g up to 6.61×106 cfu/g.There are not only spoilage organisms(Bacillus),but also pathogen pathogenic bacterium(Enterobacter)in pre-ensiled straw.After ensilaging,the mainly putrefying bacterium is Bacillus and corruption fungi are consist of Penicillium and Fusarium.Two strains of lactic acid bacteria isolated are Lactobacillus casei and Pediococcus ethanolidurans.Spoilage organisms still in post-ensiled,we should improve fermentation process and prevention aerobic deterioration.Lactic acid bacteria isolated should more research to prepare lactic acid bacteria additive.Secondly,Lactic acid bacteria are suitable for rice straw silage fermentation had studied rarely.We find Lactobacillus helveticus and Lactobacillus bulgaricus is the best inoculant for rice straw silage.Rice straw as raw material for ensiling is difficulty because their disadvantages,such as low nutrition for microbial activities,low abundances of natural populations of lactic acid bacteria.So we investigated the effect of application of lactic acid bacteria(LAB)and chemical additives on the fermentation quality and microbial community of wilted rice straw silage.Treatment with chemical additives increased the concentrations of crude protein(CP),water soluble carbohydrate(WSC),acetic acid and lactic acid,reduced the concentrations of acid detergent fiber(ADF)and neutral detergent fiber(NDF),but did not effectively inhibit the growth of spoilage organisms.Inoculation with LABs did not improve the nutritional value of the silage because of poor growth of LABs in wilted rice straw.But LABs can improve microbial community structure during fermentation.Inoculation with lactic acid bacteria and addition of chemical materials improved the quality of silage similarly to the effects of addition of chemical materials alone.Growth of aerobic and facultatively anaerobic bacteria was inhibited by this mixed treatment and the lactic acid bacteria gradually dominated the microbial community.In summary,the fermentation quality of wilted rice straw silage had improved by addition of lactic acid bacteria and chemical materials.Mycotoxins contamination in food and crops had become a serious problem.They produced by filamentous fungi.Therefore,the measures such as inhibition the growth of moulds and down-regulate the expression level of mycotoxin synthesis genes should been carried on.Lactic acid bacteria(LAB)as the preservative were studied in research,and the results shown Fusarium oxysporum growth and spores germentation has been inhibited when co-cultivated with Lactobacillus delbrueckii spp.bulgaricus GIM 1.204.The level expression of biosythesic mycotoxin was down-regulated in addition with LAB treatment.The environment created after co-cultivated LAB,lower pH and oxygen-deficient environment,also reduce mocotoxin synthesis genes expression.Base on above results,lactic acid bacteria as potential preservative and probiotics can reduce mycotoxin accumulation safely and effectively.Residual pesticides on rice straw are an increasing concern due to excessive insecticide application,which affects the quality of rice straw silage and livestock health.We examined the dissipation of pesticide residues on straw using lactic acid bacteria(LAB).Lactobacillus casei WYS3 was isolated from rice straw that contained pesticide residues.Non-sterilized rice straw that was inoculated with L.casei WYS3 strains reduced more chlorpyrifos(CP)after ensiling compared with rice straw that was not inoculated with L.casei WYS3 strains or sterilized rice straw.In pure culture,these strains can bind chlorpyrifos(CP)as indicated by HPLC analysis.The binding rate of viable L.casei WYS3 strains to chlorpyrifos is 33.30%-42.00%.These results are similar to those of acid-treated cells but less than those of heated strains,which have binding rates of 32.00%and 77.20%,respectively.Furthermore,GC-MS analysis determined that L.casei WYS3 detoxified chlorpyrifos(CP)via P-O-C cleavage.An RT-PCR analysis determined that organophosphorus hydrolase gene expression tripled after the addition of chlorpyrifos(CP)to LAB cultures compared with the control group(without chlorpyrifos).This paper highlights the potential use of lactic acid bacteria(LAB)strain starter cultures for the cleanup and detoxification of chlorpyrifos residues in the environment.