Bioconversion Of Isoflavones In Synbiotic-Soymilk Using Physical Treatments (Ultrasonication, Electroporation And Ultraviolet) On Lactobacilli And Bifidobacteria
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Date
2012-02
Authors
Yeo, Siok Koon
Journal Title
Journal ISSN
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Publisher
Universiti Sains Malaysia
Abstract
Fifteen strains of lactobacilli and bifidobacteria were screened for growth in soymilk. L. casei FTDC 2113, L. acidophilus FTDC 8033, L. acidophilus BT 4356, L. casei BT 1268, Bifidobacterium sp. FTDC 8943 and B. longum FTDC 8643 exhibited higher (P<0.05) viability and were thus selected for subsequent analyses involving prebiotics such as fructooligosaccharides (FOS), inulin, mannitol, maltodextrin and pectin. All selected strains showed viability exceeding 7 Log10 CFU/mL upon fermentation in soymilk at 37 oC for 24 h and was higher upon supplementation with maltodextrin, mannitol and FOS.
Supplementation of prebiotics also increased angiotensin I-converting enzyme (ACE)-inhibitory activity. In addition, supplementation with prebiotics such as pectin also enhanced the extracellular β-glucosidase. The intracellular β-glucosidase activity was enhanced upon supplementation with pectin and mannitol. This led to a higher bioconversion of glucosides to aglycones in soymilk supplemented with these prebiotics. Among the prebiotics, mannitol showed a more prominent effect on promoting the production of bioactive aglycones in soymilk.
Therefore, mannitol-soymilk was used for subsequent evaluations upon application of ultrasound (20-100 W; 1-3 min), UV radiation (UVA-UVC, 30-90 J/m2) and electroporation (2.5-7.5 kV/cm; 3-4 ms). These physical treatments significantly promoted the viability of lactobacilli and bifidobacteria in mannitol-
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soymilk mainly due to enhanced membrane permeability of cells upon treatments. Such changes were attributed to lipid peroxidation and alteration on membrane phospholipids bilayer. Such physical treatments also significantly promoted the intracellular and extracellular β-glucosidase activities of lactobacilli and bifidobacteria, and subsequently enhanced the bioconversion of glucosides to aglycones in mannitol-soymilk (P<0.05). Electroporation at 7.5 kV/cm for 3.5 ms showed a more prominent effect where concentrations of aglycones was increased by 78.2% compared to the control and this was clearly observed in mannitol-soymilk fermented by B. longum FTDC 8643. Ultrasound (60 W; 3 min) and UV radiation (UVB; 90 J/m2) also effectively promoted the concentrations of aglycones and was most prevalent in mannitol-soymilk fermented by L. casei FTDC 2113 (43.1-46.7% higher compared to that of the control). These treatments and strains were then selected for analyses involving inheritance potential by subsequent subcultures.
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Keywords
Bioconversion of isoflavones in synbiotic-soymilk , physical treatments on lactobacilli and bifidobacteria