Preparation And Utilization Of Oligosaccharides From Bamboo Shoots

Bamboo shoots are a healthy food with a variety of physiological activities and are widely loved by people.However,at present,the application of bamboo shoots mainly stays in direct consumption or simple overall processing,and the application surface is narrow.Moreover,the dietary fiber content of bamboo shoots is very high no matter in winter or spring.Bamboo shoot polysaccharides are a good source of functional oligosaccharides.Functional oligosaccharides have many beneficial physiological activities to the human body,and they are widely used.The traditional preparation methods of functional oligosaccharides,such as acid-base hydrolysis and enzymatic hydrolysis,have the disadvantages of low yield,high cost,and pollution to the environment.However,direct microbial fermentation is highly efficient and environmentally friendly.Cellulose is the most abundant renewable biomass resource in nature,but its dense structural characteristics limit the application of cellulose,and ionic liquid treatment of cellulose can promote the further application of cellulose.In this study,Trichoderma（MLG23）obtained through preliminary experiments fermented bamboo shoot meat powder（bamboo shoot powder）and bamboo shoot shell powder,prepared water-soluble bamboo shoots functional oligosaccharides（FOB）and bamboo shoot shell functional oligosaccharides（FOBS）,analyzed the influence of fermentation conditions on FOB and FOBS yield,and compared the differences in composition of raw materials compared with fermentation residues.The solubility characteristics of cellobiose in 1-butyl-3-methylimidazolium halide（Bmim X）ionic liquids were analyzed by ¹³C NMR technology.Finally,a trial was made to use FOB in the preparation of healthy biscuits containing functional oligosaccharides and compared with bamboo shoot powder biscuits directly added with unfermented bamboo shoot powder.The main conclusions are as follows:（1）The yield of FOB was higher than that of FOBS under different fermentation conditions.The main reason for limiting the yield of FOBS was that the ability of Trichoderma to utilize bamboo shoot shells was relatively weak.Substrate concentration was the factor that had the greatest influence on FOB and FOBS,achieving higher yields at lower feedstock volumes and decreasing slowly as substrate concentrations increase.The yield of FOB and FOBS was the highest at the fermentation temperature of 30°C.The optimum fermentation time for FOB was 4days,and the optimum fermentation time for FOBS was 2 days.Fermentation of bamboo shoot powder and bamboo shoot shells by Trichoderma to produce FOB and FOBS had great development potential in the field of commercial application.（2）After the raw materials were fermented and treated with Trichoderma,the crystallinity of the cellulose of the raw materials increased.Trichoderma’s utilization of polysaccharide components in raw materials was mainly concentrated in the amorphous region of cellulose and hemicellulose.The prepared FOB and FOBS contained certain metal salt components,which were derived from inorganic salts added in the fermentation broth,and the K metal element content was high.（3）Both the anions and cations of Bmim X formed hydrogen bonds with cellobiose,but the formation of hydrogen bonds between anions and cellobiose was a key factor in the dissolution of cellobiose in ionic liquids.The order of strength and weakness of Bmim Cl,Bmim Br and Bmim I to form hydrogen bonds with cellobiose was Bmim Cl>Bmim Br>Bmim I.（4）The strength of hydrogen bonds formed between hydroxyl groups and ionic liquids at different positions on cellobiose was different,and the strength of hydrogen bonds formed between hydroxyl groups and ionic liquids at the same location was affected by the electronegativity and volume of anions.Compared with the secondary alcohol hydroxyl group in other locations,the primary alcohol hydroxyl groups（C6-OH and C12-OH）on the glycose pyranose ring of cellobiose were more likely to form hydrogen bonds with ionic liquids,and the hydrogen bond formed by C6-OH at the reducing end was stronger than that with the non-reducing end C12-OH.（5）The addition of FOB had a great influence on the texture properties of biscuits,resulting in a decrease in hardness,crispness,elasticity,cohesion,adhesion,chewiness,and recovery.Adding FOB in a large amount could affect the taste of biscuits and increased the difficulty of preservation.A small amount of FOB addition had little effect on the taste,color,smell,etc.of biscuits,and the taste was similar to that of biscuits without addition,and there was no obvious sweetening effect.The effect of FOBS addition on the texture and taste of biscuits was similar to that of FOB.