Study On Preparation Of Lactic Acid By Inulinase Hydrolysate

Jerusalem artichoke?Helianthus tuberosus L.?,has a fleshy stem,which is used in traditional Chinese medicine for blood-cooling and dehumidification.As scenery and animal feed,it is also found that some bioactive ingredients can be extracted from its leaves and stems.More recently,a renewed and rapidly growing interest is for the use of Jerusalem artichoke tubers,which are rich in inulin,as raw materials for the extraction polysaccharides and enzymolysis.For the further development and utilization of Jerusalem artichoke,the inulin was extracted,optimized conditions of inulinase enzyme production,and liquid for the preparation of lactic acid.Mainly includes the following:According to the detection of Jerusalem artichoke it is concluded that fresh Jerusalem artichoke moisturecontent is 75.76%,other material accounted for 24.24%.Water extraction was used to abtain the inulin,and the extraction procedure was optimized using Response Surface Analysis method.The results showed that the optimum extraction conditions were as follows:liquid-solid ratio 18?1?mL/g?,extraction times 41 min and extraction temperature 85?.Under the conditions,the optimum extracting yield of inulin was 40.56%,which is well matched with the predictive extracting yield 40.74%.Under the condition of the process,to carry out the rough inulin and extraction of inulin was analyzed by Infrared spectrum.Monosaccharide composition of inulin was carried out using acid hydrolysis and acetylation,combined with GC-MS,The results showed that the inulin was composed of fructose?93.03%?and glucose?6.97%?.A preponderant inulinase strain A-15 was screened from the rhizosphere soil of Jerusalem artichoke,and the strain was identified as Aspergillus niger by the morphology and phylogenetic tree.The optimization of medium contents and fermentation conditions for Aspergillus niger A-15 to form inulinase was conducted.The optimum medium were:The best nitrogen source was 1.0%?W/V?yeast extract,0.5%of NaCl,0.3%of K₂HPO₄,constanting volume with Jerusalem artichoke juice,fermentation pH 6,temperature 30?and fermentation time of 6 days.The content of reducing sugar in Jerusalem artichoke juice was 0.997 g/L and 24.22 g/L after enzymolysis,which indicated that strain A-15 has the good performance in the degradation of Jerusalem artichoke inulin.Preparation of lactic acid?DL?using inulinase hydrolysate,and the conditions of lactic acid production was optimized using Orthogonal Method.There four strain?No.B2,zh,C2,C3?were used for lactic acid production and two unknown strains B2 and strain zh was identified as Lactobacillus casei and Lactobacillus plantarum by the morphology and phylogenetic tree.Finally choose strain B2?Lactobacillus casei?and strain C3?Lactobacillus casel subsp.pseudoplantarum?mixed fermentation lactic acid.The results showed that the optimum medium composition were as follows:0.6%soy flour,K₂HPO₄ 2.5 g/L,MnSO₄ 0.4 g/L,NaAc 6 g/L,inoculation1.5%,pH 6.5,calcium carbonate addition 2%,36?shake flask fermentated 90 h,lactic acid yield 53.28?g/100g dry matter?.In addition,the content of D-and L-lactic acid in mixed fermentation liquid was 39.38%and 60.62%analysised by HPLC.In this study,the inulin was extracted from Jerusalem artichoke and its monosaccharide composition was analyzed.A dominant strain of inducible inulin was screened and identified.The lactic acid was further studied by using inulin hydrolyzate.The systems and methods migh also be suitable for the fermentations using burdock,dahlia and other rich in inulin as the producing strains.The inulin hydrolysis sugar might also be suitable for the production of other products such as ethanol and butanol.This investigation has provided a referene for the produetion of several Produets from one starting no-gain material.