Effect Of Chitooligosaccharides On Strawberry Preservation And Its Mechanism

Corruption and excessive softening of post-harvest frui will cause serious economic losses, the preservation of post-harvest fruit play an important role in decrease the loss.Chitooligosaccharides (COS) , an effective plant inducer, have been widely used in agriculture, but the research on strawberry is limited to apparent quality, and its mechanism is still unclear. In order to explore its mechanism of fruit, this paper study the mechanism of COS on Fengxiang strawberry as the research object. The results are as follows: COS treatment can delay the postharvest storage quality of strawberry fruit, and the freshness mechanism of strawberry by COS treatment: cell wall degradation and ethylene synthesis related enzyme, ethylene glycolase (ACO),ethylene synthase (ACS), pectin lyase (PL), pectinase (PE), endoglucanase (EG),a-mannosidase(a-Man) and ?-hexosaminidase (?-Hex) were studied. The results show 1. 100mg/L COS treatment can effectively extend the strawberry storage time, keep the strawberry shelf life and quality. After 4 days treatment, the decay strawberry was lower than the control 19.35%, the content of suger and titratable acid was higher than the control 15.15%, 2.17%, respectively.2. The treatment of strawberry with 100mg/L COS can effectively delay the decrease of antioxidant activity during strawberry storage, and delay the decline of fruit quality.After 4 days treatment, the content of Vc, DPPH, anthocyanin, flavonoids and total phenol was higher than control 1.25, 1.66, 1.41, 1.24 and 1.12 times, respectively.3. The expression of PL, PE, EG, ACO, ACS, a-Man, ?-Hexl and ?-Hex2 in the storage process of strawberry can significantly reduce by COS treatment. Delay the decline in fruit hardness.4. In this paper, ?-Man is successfully cloned by gene cloning technique, but failed to express in Escherichia coli.?-Hexl and ?-Hex2 were successfully cloned by RF-Cloning technique and expressed in Pichia pastoris X-33 and then purified by nickel affinity chromatography. The two enzymes are the most active in pH4, pH5, 50?. The ?-Hexl and ?-Hex2 enzymes expressed by Pichia pastoris were identified as N-linked glycoproteins by using endosulfanase PNGase.The above results show that COS can effectively regulate the maturation and senescence of fruits, thus prolonging the storage period of fruit.