Study On Antioxidant And Antimicrobial Activities Of Peptides Derived From Fermented Foxtail Millet

Millets are a major food source in arid and semi-arid parts of the world. Millets are goodsources of energy. They provide protein, fatty acids, minerals, vitamins, dietary fibre andpolyphenols. Typical millet protein contains high quantity of essential amino acidsespecially the sulphur containing amino acids (methionine and cysteine). Processing milletcausingenhance the viability or functionality of probiotics with significant health benefits.Traditionally fermented foods and beverages obtained from millet or millet mixed withother cereals (corn and sorghum) include koko (millet porridge), fura, mangishi, jandh, uji,burukutu, kunu-zaki, ogi and bushera while dambu, masvusvu and roti are representativesof unfermented millet based products. Solid-state bioprocessing of foxtail millet byLactobacillus paracasei Fn032is a biotechnological strategy to produce fermented foxtailmillet meal with more beneficial components.The effect of L. paracasei Fn032fermentation and heat-moisture treatment (HMT)on the physicochemical properties of foxtail millet (Setaria italica) flour was investigated.The results obtained showed a significant (P <0.05) increase in proximate chemicalcomposition in general after fermentation and HMT. Differential scanning calorimetryanalysis showed high decomposition temperature (Td) trend of180.59and189.82oC afterHMT. However, there was significant (P <0.05resulted in variation of slow digestible starch and resistant starch count from6.83to18.42%and7.61to22.68%respectively, after fermentation and HTM. Following this observation,it was ascertained that in X-ray diffraction; pasting viscosity and fluorescencespectrophotometry show greater HMT influenced on the flour components. Findings fromthe scanning electron microscopy analysis showed microstructure differences of the flourssamples.Evaluation of antioxidant, antimicrobial properties and nutritional values of waterextracts from fermented foxtail millet flour and its bran with and without protease by L.paracasei Fn032was done. Fermented foxtail millet flour with added protease extractshowed higher scavenging ability on DPPH radicals as well as reducing power than fermented foxtail millet flour and fermented foxtail millet bran extracts. Both extracts,fermented foxtail millet flour and fermented foxtail millet flour with protease, showedsignificant (P <0.05) effectiveness inhibition abilities on microbial growth whencompared with fermented foxtail millet bran extracts. Amino acid profile revealed thatfermented foxtail millet flour with protease, with relatively strongest antioxidant,antimicrobial activity, also had the highest total hydrophobic amino acids content (51.39%)and hydrophobic index (8.47Kj/moL amino acid residue). Moreover, fermented foxtailmillet flour with protease revealed the highest protein content, predicted protein efficiencyratio, and protein digestibility. Molecular weight of the whole extracts varied from180–5000Da.Purification by RP-HPLC and amino acid sequencing by LC-MS of peptidesderived from foxtail millet (Setaria italica) meal fermented by L. paracasei Fn032werecarried out. The purified foxtail millet peptide fractions (FFMp) of Tyrosine/Leucine-rich(FFMp4=756.84, FFMp6=678.74and FFMp10=678.87Da) showed significant (P <0.05)scavenging activities for DPPH, and superoxide anion radicals. FFMp peptides(synthesized) have shown fairly inhibition of the Escherichia coli ATCC8099growth.Furthermore, FFMp4and FFMp6peptides showed resistance to trypsin proteolysis whileFFMp10appeared to have partial hydrolysis.The effect of chemically synthesized short peptides (6residues), previouslyidentified from a fermented foxtail millet meal fraction (FFMp10) on the cell surfacehydrophobicity (CSH), biomass growth, DNA binding ability of Escherichia coli ATCC8099was verified. The proteolytic responses of these peptides were also tested using thehigh performance liquid chromatography. Changes made in the FFMp10sequence were:Mp1, Mp2, Mp3and Mp4peptides sequences by Arg and Lys amino acids substitutions.The results revealed that all the peptides resisted to pepsin treatment for1h. However,Mp2, Mp3and Mp4showed no significant HPLC elution profile changes after the trypsintreatment. The values of CSH were significantly higher (P <0.05) with FFMp10, Mp1andMp22h treatment on bacteria, whereas, lowered with Mp3and Mp4treatment. Overallpeptides treatment lowered the rate of bacterial biomass growth when compared to control.Slight E. coli ATCC8099DNA bindings were observed in lane2,3and lane3respectivelyfor Mp1and Mp2incubation. Fermentation and heat moisture treatment methods present a possible way ofchanging or improving the physicochemical properties and add nutritional value to foxtailmillet meal. Fermented foxtail millet flour extracts were relatively effective in theantioxidant, antimicrobial properties assayed. Indeed, it is feasible to derive naturalantioxidants peptides along with antimicrobial activity and resistance to enzyme fromfermented foxtail millet meal.