Preparation Of Polysaccharide/Nano-Selenium Complex From Agrocybe Cylindracea Spent Mushroom Substrate And Its Promoting Effects On Rice Growth

Spent mushroom substrate is the residual mushroom substrate after cultivation of edible fungi.It has high utilization value because its components contain some strong biological activities such as carbohydrates,organic acids,and bioactive enzymes.China is a large producer of edible fungi with annual production of millions of tons,but the rational utilization and development of mushroom bran have not been solved.In this study,Agrocybe cylindracea was used as raw material,polysaccharide was extracted from mushroom bran,and nano-selenium complex was prepared by using mushroom bran polysaccharide as template.The growth promoting effect of spent mushroom substrate polysaccharide/nano-selenium complex on rice was explored.The main results were as follows:（1）Polysaccharides were extracted from Agrocybe cylindracea powder by hot water extraction method.The yield of polysaccharides was 11.8%.The total sugar content,ash content,fat content and polyphenol content of polysaccharides were75.15%,1.7%,2.23%and 0.02%,respectively.The results of antioxidant activity determination in vitro showed that polysaccharide had good antioxidant capacity and could effectively scavenge free radicals.Two main polysaccharides（SMS-1 and SMS-2）were isolated and purified by DEAE-Cellulose-52 and Sephadex G-100chromatography.The results of UV scanning showed that there were no obvious nucleic acid and protein absorption peaks in the polysaccharide components.The results of infrared spectroscopy showed that the polysaccharide components SMS-1 and SMS-2had typical characteristic absorption peaks of polysaccharides,and SMS-1 also had pyran rings andβ-glycosidic bonds.The polysaccharide components were scanned by UV to obtain that there was no nucleic acid or protein.The infrared absorption results showed that both SMS-1 and SMS-2 had typical characteristic absorption peaks of polysaccharides,and SMS-1 also had pyran ring andβ-glycosidic bonds.The monosaccharide composition of polysaccharides was analyzed by gas chromatography.The results showed that SMS-1 was composed of mannose,glucose and galactose,and SMS-2 was composed of mannose,xylose and galactose.（2）The spent mushroom substrate polysaccharide obtained by hot water extraction was used as stabilizer and adsorbent to prepare the spent mushroom substrate polysaccharide/nano-selenium complex.The conditions for preparing the mushroom bran polysaccharide-nano-selenium complex,the antioxidant capacity and the effects of different adding ways of spent mushroom substrate polysaccharide/nano-selenium complex on the growth of rice were explored.The results showed that homogeneous and stable spent mushroom substrate polysaccharide/nano-Selenium complex could be obtained when the proportion of polysaccharide from Agrocybe chaxingu bran was10%,the ratio of Vc to sodium selenite was 4:1,the reaction time was 4 h,and the reaction temperature was 50°C.With high antioxidant activity in vitro,the IC50 of scavenging hydroxyl free radical,superoxide anion free radical and DPPH free radical was significantly lower than the spent mushroom substrate polysaccharide.Polysaccharide/nano-selenium complex significantly promoted the germination potential and germination rate of rice seeds.Spraying 20 mg·m L^-1spent mushroom substrate polysaccharide/nano-Selenium complex on the leaf surface increased the soluble sugar content of rice compared with adding spent mushroom substrate polysaccharide/nano-Selenium complex on the root.The content in the leaves increased by 250%compared with the control group.The soluble protein content in the leaves was three times higher than that of the control group.The chlorophyll a,chlorophyll b and carotene increased by 67%,58%and 21%compared with the control group,respectively.（3）The root activity,proline content and antioxidant enzyme activity of rice were improved to some extent by foliar spraying different concentrations of polysaccharide/nano-selenium complex from spent mushroom substrate.The results showed that the root activity of 20 mg·m L^-1 polysaccharide/nano-selenium complex from spent mushroom substrate sprayed on leaves increased by 36.37%compared with the control group.In addition,the polysaccharide/nano-selenium complex from spent mushroom substrate also increased the activities of SOD,POD,CAT and other antioxidant enzymes to varying degrees,reduced the content of MDA in rice seedlings,and enhanced the stress resistance of rice.At the same time,with the increase of rice growth cycle,the effect of foliar spraying of polysaccharide/nano-selenium from spent mushroom substrate on rice growth was more obvious.When the treatment was added to the 25th day,the N,P,and K contents in each organ of the rice seedlings were increased,and were significantly higher than those of the rice seedlings without spraying the polysaccharide/nano-selenium complex from spent mushroom substrate.The determination of trace elements in the aboveground and underground parts of rice by atomic absorption spectrometry showed that the low concentration of polysaccharide/nano-selenium complex from spent mushroom substrate significantly promoted the contents of Fe,Mn,Cu,Zn and other trace elements in rice,and the accumulation amount was much higher than that in the blank control group.