| Chitin is a natural polymer nolecule whose molecular formula is(C8H13NO5)n.It is a kind of natural polymer and a renewable resource.The molecular structure of chitin and its derivatives is unique.It has a variety of functions and characteristics,and has great potential for application development in the food industry,biomedicine,cosmetics,agriculture,textile industries,etc.At present,the traditional large-scale production of chitin is mostly made from shrimp and crab shells.However,the purity of extracted chitin is difficult to be up to the industrial and food-grade standard because of the difficulty in removing ash from shrimp and crab shells.Previous studies of extracting chitin have mainly focused on insects.Monochamus alternatus(Hope),Pine sawyer beetle(Coleoptera:Cerambycidae)is an important pest of the genus Pinus and the dispersing vector of the nematode Bursaphelenchus xylophilus in China.Once infected,Masson pines(Pinus massoniana Lamb.)will die within two to three months.Compared with other insects,pine sawyer beetle is a better resource for chitin,because it has a higher degree of chitinization,and numerous chitin.In view of this,this paper used M.alternatus as the raw material,and the relnoval rate of ash and protein was the evaluation index.First,the high-quality strains and proteases were determined by single-factor experiments,and then the best fermentation conditions and enzynolysis conditions were selected.Furthermore,the chitin was extracted by the "Bacterium-Protease Combined Method".Finally,the chitin extracted was compared with the traditional "acid-alkali method" for the analysis of chitin using infrared spectroscopy to explore the feasibility and application prospects of the extraction of chitin by "Bacterium-Protease Combined Method".The main results are as follows,1.The best strain was Bacillus coagulans.The best fermentation conditions:M.alternatus powder concentration was 8%,glucose concentration was 80,inoculation amount of B.coagulans was 11%,and shaking speed was set to 100r/Min,the fermentation temperature was 47℃,and the average removal rate of final ash can reach 91.72%after 5 days of fermentation.Orthogonal experimental results showed that:When the control glucose concentration was 8%,the shaking speed was 100r/min,the inoculation amount of B.coagulans was 11%,the fermentation temperature was 52oC,and the fermentation time was 5 days,the maximum ash removal rate was achieved.At this time,the average removal rate of ash could reach 90.38±0.30%.2.The best protease was proteinase K,the best conditions for the hydrolysis:M.alternatus powder concentration was 8%,the amount of proteinase K added was 800U/g,the pH of the suspension was adjusted to 8.0,the enzymolysis temperature was at 55℃,the enzymolysis time was 9h,and the final protein removal rate could reach 82.71 ±0.82%.3.The best conditions for combined fermentation:8%M.alternifolius powder,8%glucose liquid medium,inoculation of 11%B.coagulans,setting a constant temperature shaker temperature of 50℃,and a shaking speed of 100r/min,At the same time,the protease K and B.coagulans were added for 5 days.The final yield of chitin was 32.51%,the purity of the chitin in the product was 72.78%,the residual ash content was 1.42%of the chitin product,and the protein residue accounted for 25.74%of the chitin product.4.Infrared spectroscopic identification results indicated that the chitin extracted using the"Bacterium-Protease Combined Method" and the traditional "acid-base method" can basically maintain the molecular characteristics of the standard chitin,but the "|acid-base method" extracted chitin appeared two new peaks.It has a big difference from standard chitin.Therefore,it is more advantageous to obtain chitin by the "Bacterium-Protease Combined Method". |
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