Integrated Utilization of Dairy Whey in Probiotic β-Galactosidase Production and Enzymatic Synthesis of Galacto-Oligosaccharides

Feiyu Duan,Lili Lu,Jingyi Yang,Renfei Zhao,Min Xiao

doi:10.3390/catal11060658

Feiyu Duan, Lili Lu + Show 3 more

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https://doi.org/10.3390/catal11060658

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Abstract

This work established an integrated utilization of dairy whey in β-galactosidase production from Lactobacillus bulgaricus and prebiotics synthesis by the probiotic enzyme. A cost-effective whey-based medium was newly developed for culturing Lactobacillus bulgaricus to produce β-galactosidase. The medium was optimized through response surface methodology (RSM) involving a series of statistical designs, such as the Plackett–Burman design, steepest ascent experiment, and central composite design. Under the optimized medium, the β-galactosidase activity of L. bulgaricus reached 2034 U/L, which was twice that produced from the traditional MRS medium. The cells of L. bulgaricus harvested from the whey-based medium were subsequently treated with lysozyme. The resulting crude enzyme was used as an efficient catalyst, which catalyzed the synthesis of the prebiotic galacto-oligosaccharides (GOS) in a high yield of 44.7% by using whey (200 g/L) as the substrate. The sugar mixture was further purified by activated charcoal adsorption, thereby yielding a high-purity level of 77.6% GOS.

Highlights

The nutritional factors suitable for producing β-galactosidase by L. bulgaricus L3 were preliminarily screened by the individual addition of the MRS components to the whey broth in order to evaluate their effects on cell growth and enzyme production
The combination of whey, inorganic salts, and yeast powder resulted in higher biomass of bacteria and enzyme activity, compared with the MRS medium
This work provided an integrated utilization of whey waste in L. bulgaricus cell growth, β-galactosidase production, and GOS synthesis

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Galacto-oligosaccharides (GOS) are a well-known class of probiotics with functions resembling human milk oligosaccharide. GOS have various benefits for the human health, including the selective stimulation of the beneficial intestinal bacteria growth, maintenance of the normal flora balance in the intestine, increase in Ca2+ absorption, and decrease in serum cholesterol levels and cancer risks [1,2]. GOS can act as receptor decoys and exhibit direct anti-infective functions by binding pathogens and helping flush them out of the gastrointestinal tract due to the structural similarity to the pathogen receptors [3]

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