Aspergillus flavus is a toxigenic fungus well known for the synthesis of aflatoxins that contaminate crops and food products. Antifungal peptides generated by lactic acid bacteria have a high potential for applications as biocontrol agent to prolong the shelf life of crops. In this study, antifungal activity of peptides generated by Lactobacilli's plantarum TE10 was tested against the spoilage fungi Aspergillus flavus MD3. L. plantarum TE10 was inoculated in MRS broth and incubated at 37 degrees C for 48 h and the antifungal activity was determined using dual agar overlay method. The cell free supernatant was fractionated using size exclusion chromatography, and the peptides were identified using LC-MS/MS. Scanning electron microscope was performed to determine the effects of the active fraction on the morphology of target fungi. The antifungal activity of the active fraction was further confirmed against selected fungi in fresh maize seeds. A total of 37 peptides were identified in fraction 7 that showed the highest antifungal activity. The peptides mixture in fraction 7 caused damage at the tip of the mycelia as observed by scanning electron microscope. Growth of A. flavus was observed after 7 days on the samples treated with distilled water and MRS broth, while slight growth was observed on the sample treated with fraction 7. Fraction 7 reduced the spore formation of A. flavus by 4 folds compared to the control. The results demonstrated promising application of the peptides mixture as bio-control agent to prevent the growth of A. flavus in maize.

Aspergillus flavus is a toxigenic fungus well known for the synthesis of aflatoxins that contaminate crops and food products. Antifungal peptides generated by lactic acid bacteria have a high potential for applications as biocontrol agent to prolong the shelf life of crops. In this study, antifungal activity of peptides generated by Lactobacilli's plantarum TE10 was tested against the spoilage fungi Aspergillus flavus MD3. L. plantarum TE10 was inoculated in MRS broth and incubated at 37 degrees C for 48 h and the antifungal activity was determined using dual agar overlay method. The cell free supernatant was fractionated using size exclusion chromatography, and the peptides were identified using LC-MS/MS. Scanning electron microscope was performed to determine the effects of the active fraction on the morphology of target fungi. The antifungal activity of the active fraction was further confirmed against selected fungi in fresh maize seeds. A total of 37 peptides were identified in fraction 7 that showed the highest antifungal activity. The peptides mixture in fraction 7 caused damage at the tip of the mycelia as observed by scanning electron microscope. Growth of A. flavus was observed after 7 days on the samples treated with distilled water and MRS broth, while slight growth was observed on the sample treated with fraction 7. Fraction 7 reduced the spore formation of A. flavus by 4 folds compared to the control. The results demonstrated promising application of the peptides mixture as bio-control agent to prevent the growth of A. flavus in maize.

Stichopus horrens flesh was explored as a potential source for generating peptides with angiotensin-converting enzyme (ACE) inhibitory capacity using 6 proteases, namely alcalase, flavourzyme, trypsin, papain, bromelain, and protamex. Degree of hydrolysis (DH) and peptide profiling (SDS-PAGE) of Stichopus horrens hydrolysates (SHHs) was also assessed. Alcalase hydrolysate showed the highest DH value (39.8%) followed by flavourzyme hydrolysate (32.7%). Overall, alcalase hydrolysate exhibited the highest ACE inhibitory activity (IC50 value of 0.41 mg/mL) followed by flavourzyme hydrolysate (IC50 value of 2.24 mg/mL), trypsin hydrolysate (IC50 value of 2.28 mg/mL), papain hydrolysate (IC50 value of 2.48 mg/mL), bromelain hydrolysate (IC50 value of 4.21 mg/mL), and protamex hydrolysate (IC50 value of 6.38 mg/mL). The SDS-PAGE results showed that alcalase hydrolysate represented a unique pattern compared to others, which yielded potent ACE inhibitory peptides with molecular weight distribution lower than 20 kDa. The evaluation of the relationship between DH and IC50 values of alcalase and flavourzyme hydrolysates revealed that the trend between those parameters was related to the type of the protease used. We concluded that the tested SHHs would be used as a potential source of functional ACE inhibitory peptides for physiological benefits.

The use of secondary metabolites of lactic acid bacteria for preservation of foods is increasingly gaining interest to the food industry to replace synthetic preservatives. In this study, the cell free supernatant containing peptides obtained from Lactobacillus plantarum IS10 was fractionated by size exclusion chromatography using sephadex G-25, and tested against Aspergillus flavus MD3, Penicillium rogueforti MD4 and Eurotium rubrum MD5. Among the fractions, fraction number 10 showed 60% antifungal activity at a concentration of 0.02 mg peptide/mL. Four novel peptides out of twenty peptides obtained from fraction 10 were identified and determined by de novo sequencing. Peptide FPSHTGMSVPPP with a net charge +1, hydrophobicity ratio 58% and molecular weight of 1253 was further studied. The selected peptide showed a good activity at a concentration of 5 mg/mL against selected fungi and poor activity at low concentrations. This work indicates that L plantarum IS10 has the capability of producing peptides which are affective against spoilage fungi. (C) 2015 Elsevier Ltd. All rights reserved.

Bio-preservation, a promising preservation method that involves the use of "friendly" microorganisms such as lactic acid bacteria, has recently become a topic of considerable interest. In the present study, 16 lactic acid bacteria isolates were evaluated for antifungal activity against six fungi commonly associated with bread spoilage. The antifungal compounds were heat stable at 121 A degrees C, and only four isolates, DU15, IT10, TE10, and IS10, showed partial loss of activity when supernatants were treated with proteolytic enzymes. The four isolates showed high inhibition activity at pH 3 and were identified using 16S rDNA sequencing as belonging to Leuconostoc mesenteroides DU15, Lactobacillus plantarum TE10, Lactobacillus plantarum IT10, and Lactobacillus plantarum IS10. The minimum germination inhibitions were 30 mg, 50 mg, 40 mg, and 50 mg for TE10, IT10, DU15, and IS10 respectively. The optimum conditions for the strains to produce antifungal compounds were 37 A degrees C for 48 h for IT10, IS10, and TE10, and 30 A degrees C for 24 h for DU15. Antifungal activity was increased threefold when supernatants were filtered using 10 KDa membranes. These findings demonstrate the potential of using lactic acid bacteria antifungal peptides as natural preservatives in bakery products to control the growth of spoilage fungi.

The ability of Leuconostoc mesenteroides DU15 to produce antifungal peptides that inhibit growth of Aspergillus niger was evaluated under optimum growth conditions of 30 degrees C for 48 h. The cell-free supernatant showed inhibitory activity against A. niger. Five novel peptides were isolated with the sequences GPFPL, YVPLF, LLHGVPLP, GPFPLEMTLGPT, and TVYPFPGPL as identified by de novo sequencing using PEAKS 6 software. Peptide LLHGVPLP was the only positively charged (cationic peptides) and peptide GPFPLEMTLGPT negatively charged (anionic), whereas the rest are neutral. The identified peptides had high hydrophobicity ratio and low molecular weights with amino acids sequences ranging from 5 to 12 residues. The mode of action of these peptides is observed under the scanning electron microscope and is due to cell lysis of fungi. This work reveals the potential of peptides from L. mesenteroides DU15 as natural antifungal preservatives in inhibiting the growth of A. niger that is implicated to the spoilage during storage.