Antioxidant and Antibacterial Peptides from Soybean Milk through Enzymatic- and Membrane-Based Technologies

Abstract

Enzymatic hydrolysis of soybean milk proteins with cysteine protease papain was performed in an advanced bioreactor, operated with batch mode. In soybean milk protein hydrolysis reaction, enzyme and substrate ratio and reaction temperature were varied, ranging from 0.029:100-0.457:100 and 30-60 • C, respectively. The degree of hydrolysis of soybean milk proteins was increased with increase of enzyme and substrate (soybean milk protein) ratio. However, the degree of hydrolysis was increased due to change of reaction temperature from 30 • C to 60 • C with enzyme and substrate ratio 0.229:100 and was reduced when hydrolysis reaction was performed with enzyme and substrate ratio 0.11:100 at hydrolysis temperature 60 • C. Antioxidant capacity of enzyme-treated milk had a similar trend with degree of hydrolysis. In a later exercise, a membrane bioreactor was adopted for continuous production of antioxidant and antibacterial peptides from soybean milk. The membrane bioreactor was operated for 12 h with constant feeding. Ceramic-made tubular membrane with a pore size 20 nm was used. Application of static turbulence promoter in a membrane separation process was investigated and its positive effects, with respect to higher permeate flux and lower energy consumption in filtration process, were proven. Antioxidant capacity and antibacterial activity against Bacillus cereus of enzyme-hydrolyzed milk and permeate from membrane were confirmed.

Beneficial Effects of Soybean-Derived Bioactive Peptides

“…The physical characteristics of SPs include (1) high-concentration dissolution with low viscosity, (2) high clarity, and (3) low allergy compared with soy protein. In addition, purified SP has faster absorption into the body than amino acids [33,34]. In a recent study, the small intestine was shown to follow a separate path to absorb unmodified peptides, and it was found that relatively low-molecular peptides are absorbed [35].…”

Antioxidant Effect of Soymilk Fermented by Lactobacillus plantarum HFY01 on D-Galactose-Induced Premature Aging Mouse Model

“…Soybeans have an antioxidant function involving a variety of antioxidant components, among which isoflavones and phenolic substances have the main effect; they help delay aging, reduce cholesterol levels, regulate blood lipid levels, etc. (19)(20)(21). In soymilk fermentation, microorganisms decompose protein in the milk and change soybean isoflavone structures.…”

Production of Liquid Milk Protein Concentrate with Antioxidant Capacity, Angiotensin Converting Enzyme Inhibitory Activity, Antibacterial Activity, and Hypoallergenic Property by Membrane Filtration and Enzymatic Modification of Proteins

“…Individual batch-mode experiments were performed for protein hydrolysis process. For that purpose, 450 µL, 900 µL, 1.8 mL, and 3.6 mL of trypsin solution from stock solution (concentration of trypsin 0.009 g•mL −1 ) were injected through 0.22 µm of polytetrafluoroethylene (PTFE) syringe filter (VWR International, Pennsylvania, USA) to 500 mL of milk with concentrated proteins in bioreactor [67]. Enzymatic reaction was performed at a temperature of 40 • C for 10 min [68,69].…”

“…Enzymatic reaction was performed at a temperature of 40 • C for 10 min [68,69]. During enzymatic reaction, agitation speed in the bioreactor was maintained, 175 rpm, and the pH of milk in the bioreactor was controlled, 6.8, by automated addition of 2.0 N of sodium hydroxide or hydrochloric acid [67]. After 10 min of enzymatic reaction, 20 mL of sample was collected by a syringe from the bioreactor and kept in a sample tube.…”

“…Bacterial culture was spread on solidified agar in respective petri plates (pour plated) and agar wells with diameter 5 mm were filled with 100 µL of control milk and enzyme-treated milk samples. Petri plates were incubated at temperature 37 • C for 48 h in a biological incubator (HACH, Düsseldorf, Germany) [65,67]. The diameter of zone of inhibitions in microbial plates were measured by excluding the diameter of wells (5 mm) using a digital Vernier caliper (UEMATSU SHOKAI CO., LTD., Sendai, Japan).…”