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Defatted wheat germ peptides (DWGPs) were prepared by fermentation with Bacillus Subtilis B1 and the antioxidant activities of DWGPs were investigated. The fermentation condition was optimized by response surface method (RSM) with three factors and three levels according to Box-Behnken theory. A maximal yield of DWGPs was achieved 8.69 mg/mL under optimal conditions: inoculum size 8%, fermentation temperature 31 °C and time 48 h. The main portion in the hydrolysates after fermentation was not free amino acid but peptide. The main molecular weight distribution of DWGPs was lower than 1000 Da. A positive correlation (R(2) = 0.9911) was found between concentration of DWGPs and total antioxidant capacity (T-AOC). DWGPs presented a significant does-dependent on scavenging activities of DPPH, hydroxyl and superoxide anion radicals. The EC50 values for the scavenging rates of DPPH, hydroxyl and superoxide anion radicals were 3.16 mg/mL, 6.04 mg/mL and 7.46 mg/mL, respectively. The results suggested that DWGPs produced by fermentation could be used as a promising antioxidant ingredient.

The Maillard reaction (MR) under wet reaction conditions with several common saccharides, such as xylose, glucose, lactose, dextran and maltodextrin, were applied to improve the functional properties of wheat germ protein (WGP). The MR products (MRPs) prepared with dextran at pH 11.0 heated at 90°C in 2% aqueous dispersions heating for 20 min showed better solubility and emulsifying properties. The fluorescence intensity analysis proved the MR occurred, and thinner sheet MRPs were observed by scanning electron microscope (SEM). The relative contents of Cys, Lys and Arg were decreased, which could reduce the chance of protein aggregation through -S-S bonds. Circular dichroism (CD) spectrum expressed the difference in the secondary structures between WGP and MRPs, which may make MRPs show better functional properties than WGP. These results suggested that MR with dextran under wet reaction conditions can be a promising way to improve functional properties of WGP.

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The Jatropha curcas meal was detoxified by different methods, and the effect of detoxification was evaluated in this study. The method that hydrolysis of enzymes (cellulase plus pectinase) followed by washing with ethanol (65%) had a significant (p < 0.05) effect on the toxin, antinutritional components, and nutritional quality of proteins. After this treatment, the phorbolesters (PEs) were decreased by 100%. The antinutritional components (phytates, tannins, saponins, protease inhibitor, and lectin activities) were decreased to tolerable levels, which were lower than those in soybean meal. The crude protein in detoxified meal was 74.68%, and the total content of amino acids was 66.87 g/100 g of dry matter. The in vitro protein digestibility (IVPD) increased from 82.14 to 92.37%. The pepsin-insoluble nitrogen was only 4.57% of the total nitrogen, and about 90% of the protein was true protein. The protein-digestibility-corrected amino acid score (PDCAAS) of the meal was 0.75. The results showed that this treatment was a promising way to detoxify J. curcas meal, and the nutritional quality of detoxified meal can be simultaneously enriched and improved.

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A novel method named cell membrane affinity chromatography was used to screen antimicrobial peptides from Jatropha curcas . A cationic antimicrobial peptide (KVFLGLK, JCpep7) was successfully isolated and identified. Antimicrobial assays indicated that JCpep7 was active against the tested microorganisms ( Salmonella typhimurium ATCC 50013, Shigella dysenteriae ATCC 51302, Pseudomonas aeruginosa ATCC 27553, Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 23631, and Streptococcus pneumoniae ATCC 49619) with minimal inhibitory concentration (MIC) values ranging from 24 to 64 μg/mL. The antimicrobial mechanisms based on Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) techniques showed that JCpep7 killed microbes principally via breaking of their cell walls and membranes, followed by cell lysis. The results indicated that cell membrane affinity chromatography could be a promising approach for high-throughput screening of antimicrobial peptides from J. curcas .

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