| Chemicals such as Carbendazim, Thiabendazole, Sportak etc. are widely used to keeping litchi fresh. However, the chemicals are toxic to some degree and drug residues are not easy to remove, which is a potential threat to human's health and ecological environment. Therefore, developing the safe, non-toxic and pollution-free bio-preservative to replace the chemicals is popular in preservation industry.?-PL is a kind of natural homopolymer amino acids, and L- lysine amino is formed by alpha carboxyl and epsilon- amide linkage connected in sequence. ?-PL has broad-spectrum antibacterial activity, including gram-negative bacteria, gram-positive bacteria and phages.Because of its security and biodegradable, ?-PL is widely used in food preservatives in most countries in the world.This study for the purpose of developing biological preservatives, was focused on researching ?-PL fermented liquid biological fresh-keeping effect to litchi.white Streptomyces strain for fermentation to optimize its media and culture conditions, using its broth litchi lychee anthrax and do Peronophythora inhibition assay, and preservation effect was studied at room temperature storage environment.The test results were as follows:1. White Streptomyces fermentation ?-PL production optimization: the use of orthogonal experimental design based on the single factor experiment as well as the production of ?- polylysine medium composition a preliminary optimization. The best culture conditions were as follows: soluble starch 25 g/L, yeast extract 7 g/L, tryptone 6g/L,dipotassium phosphate 4.28 g/L, monopotassium phosphate 2.09 g/L,PH6, 30 ?, 180r/min.Under the optimum culture conditions ?-PL production reached 0.651 g/L, relative to the initial culture conditions increased by 34.62 %,( P=0.029<0.05),Bacteria biomass was8.566 g/L, relative to the initial culture conditions increased by 30.48 %,(P=0.033<0.05).2. Accroding to the litchi anthrax and litchi frost the fungus inhibition experiment,white Streptomyces fermentation liquor of litchi anthrax and litchi frost the fungus had obvious inhibitory effect. However,the litchi anthrax and litchi frost caused the fungus are litchi rot pathogen, We could indicate that fermentation of Streptomyces albus fresh litchi had antiseptic effect.3. At ambient temperature conditions, the fermentation broth for litchi fruit preservation, the results showed that this method could reduce the fresh fruit water loss,delay lychee pericarp browning, to maintain a high rate of good fruit, slowing the loss of nutrients fruit. The fruit of Feizixiao litchi storage 6 d, weight loss rate 9.42 %, good fruit rate 20 %, anthocyanin 0.046 mg/g.FW, TSS 15 %, Vc 0.386 mg/g, total sugar 116.7 mg/g,TA 0.192 %,and after the preservative treatment of Litchi Water Loss 7.93 %, good fruit rate 75 %, anthocyanin 0.052 mg/g, TSS15.5 %, Vc 0.393 mg/g, total sugar content 117.2mg/g, TA 0.195 %. Room temperature Nuomici litchi after sixth days of good fruit rate20 %,weight loss rate of 10.3 %,anthocyanin 0.058 mg/g.FW, Vc content of 0.223 g/mg,total sugar content of 127.8 mg/g, TA 0.135 %, and after the preservative treatment of litchi fruit rate was 45 %, weight loss rate of 9.7 %, anthocyanin 0.068 mg/g·FW, TSS 13.8 %, Vc0.285 mg/g, total sugar content of 129.3 mg/g, TA 0.145 %. P values Feizixiao and Litchi chinensis good fruit preservative treatment and negative control groups, respectively(P =0.022 <0.05)(P=0.034<0.05), white Streptomyces fermentation broth as a preservative significantly improve litchi good fruit.Through the above research studies, we can drop a conclusion that the method of preservation of litchi better preservation effect, and its preservation effect and chemicals(1 ‰ sportak) fairly. therefore, had the potential to replace chemical preservation. |
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