Preparation Of Tartary Buckwheat Antimicrobial Peptides By Solid State Fermentation And Its Application In Freshness

Antibacterial peptides are important substances functioning as self-defense against infection by various harmful pathogens. They are isolated from various sources among animals, plants, and bacteria, and have been characterized. Antimicrobial peptides have small molecular weight, strong antimicrobial activity, wide antimicrobial spectrum, good thermostability, good water solubility, non-talerance, and safe non-toxic advantages such as more and more are favored by the consumers. Screening of strains used for producing antibacterial peptide from tartary buckwheat by solid-state fermentation, optimization of fermentation conditions, and on the basis of the effect of preservation of tartary buckwheat antibacterial peptide of tilapia fillets were studied in detail in this paper. In order to provide a new direction for the application of tartary buckwheat, provide the theoretical basis and technical support for their mass production; at the same time provide certain reference for application of antimicrobial peptides in aquatic products preservation. The main research contents and results are as follows:1. Screening of strains used for tartary buckwheat by solid-state fermentationAspergillus oryzae, Aspergillus sojae, Actinomucor repens and Rhizopus oligosporus were a respectively applied tartary buckwheat solid-state fermentation. The protease activities, degree of hydrolysis, Peptide content, inhibition rate were regarded as evaluation indexes to verify target strains. Among these strains, Aspergillus oryzae was the most optimal strain which can be applied in tartary buckwheat solid-state fermentation to prepare antibacterial peptides. The highest peptides content was (19.26±0.55) mg/mL, which found in the tartary buckwheat of 10 g solid-state fermentation of Aspergillus oryzae of 2 days, the inhibition rate of E. coli and S. aureus were 96.62±1.66%and 97.54±0.54%respectively. According to the different molecular weight distributions and activity analysis of liquid fermentation product of Aspergillus oryzae of 2 days demonstrated that different components molecular segments had an impact on the activity of antimicrobial peptides.2. Condition optimization of solid-state fermentation process prepared tartary buckwheat antibacterial peptide On the basis of single factor test, using the Plackett-Burman test and response surface test was carried out to optimize optimum process conditions, and to prepare antibacterial peptides used for tartary buckwheat of 10 g by solid-state fermentation of Aspergillum oiyzae. The optimum process conditions were as followed:inoculums size of 1.97 mL, water addition amount of 4.06 mL, potassium hydrogen phosphate addition amount of 0.34%, fermentation time 2.17 d, peptide content in the theoretical value of 39.62 mg/mL, actual measurement value of (39.18±1.11) mg/mL, and the inhibition rate of E. coli and S. aureus were 96.62±1.66%and 97.54±0.54% respectively.3. Effect of tartary buckwheat antibacterial peptide on preservation of tilapia fillets Different concentrations of tartary buckwheat antibacterial peptides were used for preservation of tilapia fillets. Sensory evaluation, pH value, thiobarbituric acid (TBA), total volatile basic nitrogen (TVB-N) and total plate count were determined to study the tilapia fillets changes of the freshness during storage of 4 ℃.6.0 mg/mL of tartary buckwheat antibacterial peptides processed tilapia fillets freshness were prolonged 4 days, preservation time was 2 times in the control group, and preservation effect was significantly better than 10 mg/mL of Nisin.