95 - ‘Synthesis of the Cancer Preventive Peptide Lunasin by Lactic Acid Bacteria During Sourdough Fermentation’. Nutrition and Cancer. 64:1, (111-120)

Introduction

This study talks about the synthesis of a cancer preventative peptide (protein) called Lunasin by lactic acid bacteria during the process of sourdough fermentation.

Aim

This study aimed to exploit the potential of sourdough lactic acid bacteria to release lunasin during fermentation of cereal and nonconventional flours.

Method

The peptidase activities of a large number of sourdough lactic acid bacteria were screened using synthetic substrates. Selected lactic acid bacteria were used as sourdough starters to ferment wholemeal wheat, soybean, barley, amaranth, and rye flours. Proteinase activity during fermentation was characterised by SDS-PAGE analysis of the water-soluble extracts.

Results

Albumins having molecular masses of 18 to 22 kDa, which included the size of lunasin precursors, were markedly affected by proteolysis of lactic acid bacteria. After fermentation, lunasin from the water- soluble extracts was quantified, purified, and identified through RP-HPLC and nano-LC-ESI-MS analyses. Compared to control doughs, the concentration of lunasin increased up to 2–4 times during fermentation. Lactobacillus curvatus SAL33 and Lactobacillus brevis AM7 synthesized the highest concentrations of lunasin in all the flours. Besides the presence of the entire lunasin sequence, fragments containing the immunoreactive epitope RGDDDDDDDDD were also found.

Lunasin is a cancer-protective peptide, meaning it has been demonstrated to possess anti-cancer activity in animal studies. Compared to control doughs, the concentration of lunasin was shown to increase as much as 2–4 times its original levels during sourdough fermentation in wholemeal wheat, soybean, barley, amaranth, and rye flours. Lactobacillus curvatus SAL33 and Lactobacillus brevis AM7 synthesized the highest concentrations of lunasin in all the flours.