Preparation Of Biodegradable Plastic Film From Shrimp Shell And Rice Straw Fermented With Mixed Bacteria

Biodegradable mulch has the advantages of traditional mulch(heat preservation,moisture retention,moisture retention)and can avoid the disadvantages of traditional mulch(difficult to degrade and recycle),and is widely used in agriculture.The use of biodegradable mulch by biodigestion is a future trend in the study of biodegradable mulch.Rice straw and shrimp shells are agricultural solid waste with low utilization rate;rice straw is rich in cellulose polysaccharides and shrimp shells are rich in protein,which can provide rich nutrients for microbial growth.In this paper,polysaccharides prepared by co-fermentation of shrimp shells and rice straw by bacteria and fungi were used as raw materials for the production of biodegradable mulch,and modifiers were added to prepare biodegradable mulch to provide a theoretical basis for the preparation of biodegradable mulch.The main research results are as follows:(1)Samples were collected from mudflats in Yancheng(120.84°E,33.19°N),and strains of shrimp shell degrading bacteria were screened using the transparent circle method with colloidal titin plates.The target strain was observed to be round with smooth and neat edges under the light microscope,and the Gram stain showed that it was Gram-negative;the optimum salinity of the bacterium was 3% and the maximum salinity tolerance was 8%;16S identified the bacterium as Photobacterium sp.LYM-1(currently stored in the Guangdong Province Strain Conservation Center,conservation number GDMCC1.3009);the optimum pH of its chitinase is 6.0 and the optimum temperature is 30℃,and it has no antagonistic effect with the Aureobasidium pullulans(high cellulase degrading straw)in the laboratory,so it can be used for co-fermentation.(2)Polysaccharides were prepared by co-fermentation of straw and shrimp shells with the screened Photobacterium sp.LYM-1(chitinase degrading chitin)and the Aureobasidium pullulans(cellulase degrading cellulose),and the results showed that the highest cellulase enzyme activity was 115.89 U/mL and chitinase enzyme activity was17.89 U/mL during the fermentation of the mixed bacteria.The polysaccharide prepared by fermentation contained glyoxylate(12.97%),flavonoids(8.01%),polyphenols(2.20%),protein(1.31%)and ash(3.21%);and it mainly consisted of six monosaccharides: mannose,glucose,glucosamine,galactose,arabinose and ribose;the infrared spectrum showed that it had the characteristic absorption peaks of polysaccharides.The optimal process of mixed bacteria fermentation was: fermentation time 6 d,fermentation temperature 31℃,inoculum amount 10%,strain ratio 2:1(Aureobasidium pullulans : Photobacterium sp.LYM-1).(3)By measuring the tensile strength,elongation at break,water absorption and water solubility of the biodegradable ground film(PFCGl),its formulation was determined as fermented polysaccharide(4%),polyvinyl alcohol(4%),glycerol(0.15%)and citric acid(0.5%).The heat preservation and moisture retention performance test results of PFCGl indicated that it could meet the basic needs of plant growth at 10℃;soil burial test experiments showed that PFCGl lost 10.54% of its weight after 30 d of burial in soil,and the polysaccharide fraction in the film was degraded as shown by infrared spectral scan results.