Sources of β-galactosidase and its applications in food industry

3 Biotech (2017) 7:79 DOI 10.1007/s13205-017-0645-5 REVIEW ARTICLE Sources of b-galactosidase and its applications in food industry Shaima Saqib1 • Attiya Akram1 • Sobia Ahsan Halim1 • Raazia Tassaduq1 Received: 18 December 2016 / Accepted: 6 February 2017 / Published online: 12 May 2017 Ó Springer-Verlag Berlin Heidelberg 2017 Abstract The enzyme b-galactosidases have been isolated from various sources such as bacteria, fungi, yeast, vegetables, and recombinant sources. This enzyme holds importance due to its wide applications in food industries to manufacture lactose-hydrolyzed products for lactoseintolerant people and the formation of glycosylated products. Absorption of undigested lactose in small intestine requires the activity of this enzyme; hence, the deficiency of this enzyme leads to lactose intolerance. Lactose intolerance affects around 70% of world’s adult population, while the prevalence rate of lactose intolerance is 60% in Pakistan. b-Galactosidases are not only used to manufacture lactose-free products but also employed to treat whey, and used in prebiotics. This review focuses on various sources of b-galactosidase and highlights the importance of b-galactosidases in food industries. Keywords b-Galactosidase
Lactose hydrolysis
Galactooligosaccharide
Whey & Sobia Ahsan Halim ; Shaima Saqib Attiya Akram Raazia Tassaduq 1 Department of Biochemistry, Kinnaird College for Women, 93-Jail Road, Lahore 54000, Pakistan Introduction b-Galactosidase, commonly known as lactase, is an enzyme responsible to hydrolyze lactose. This enzyme has wide applications in food-processing industries. The presence of excessive lactose in intestine typically leads to tissue dehydration and reduced calcium absorption due to low acidity that causes diarrhea, flatulence, and cramps (Carrara and Rubiolo 1994; Felicilda-Reynaldo and Kenneally 2016; Vandenplas 2015; Lukito et al. 2015). Absorption of lactose requires the activity of lactase enzyme, found in small intestine that functions by splitting the bond linking the two sugars (monosaccahrides). The deficiency of this enzyme in intestine leads to lactose intolerance, and the people suffering from it are unable to consume milk and dairy products. Furthermore, the ability of this enzyme to produce a colored product during a chemical reaction has gained its importance in molecular biology (Ianiro et al. 2017; Shukla and Wierzbicki 1975). b-Galactosidase is basically a tetramer of four identical polypeptide chains with each chain consisting of 1023 amino acids which combine to form five well-defined structural domains. One of these domains is a jelly roll barrel, while the remaining domains consist of fibronectin, b-sandwich, and a central domain with TIM-type barrel that also serves as the active site (Huber et al. 1976). The central domain is catalytically active and is made of the tetramer subunits. Dissociation of tetramer into dimers inactivates the active site. The sequence at the amino terminal of this enzyme consists of a-peptide which is involved in a-complementation and plays a role in subunit interface (Corral et al. 2005). As an enzyme, b-galactosidase cleaves the disaccharide lactose to produce galactose and glucose which then ultimately enter glycolysis. This enzyme also causes 123 79 Page 2 of 7 transgalactosylation reaction of lactose to allolactose which then finally cleaved to monosaccharides. Upon binding to lacZ repressor, this allolactose regulates the amount of bgalactosidase in the cell by creating positive feedback (Pivarnik and Senecal 1995). People who are intolerant to this sugar have deficiency of b-galactosidase in their small intestine. This enzyme is present in mammals during the breast-feeding period; however, in most of the individuals, b-galactosidase activity decreases after this period, which characterizes primary hypolactasia and creates symptoms of lactose intolerance. This disorder affects about 70% of the world’s adult population. The prevalence of lactose intolerance in Western countries varies from 4 to 50%, while its prevalence in Pakistan is about 60% (Priebe et al. 2002). Industrially, b-galactosidase has various applications. Besides producing lactose-free products for lactose-intolerant individuals, b-galactosidases are also used to solve whey disposal issues on commercial scale (Karasova et al. 2002). Lactose is hygroscopic and causes crystallization in food products; hence, b-galactosidases are used to hydrolyze lactose to solve lactose-related crystallization in frozen, concentrated desserts. This treatment usually decreases lactose content of milk to be used by intolerant individuals (Champluvier et al. 1988). Furthermore, dairy whey, a byproduct of cheese industry is usually treated with this enzyme. Whey disposal has become a serious environmental issue since it is disposed into water streams, thereby causing severe water pollution (Brandão et al. 1987). b-Galactosidase are used to treat whey to convert it into useful products such as ethanol and sweet syrup that has further wide range of applications in confectionary, bakery, and other industries (Zhou and Chen 2001). The sources of b-galactosidases are microbial, vegetable, and animal origin. However, usually microbial sources show higher productivity, and consequently, using them results in reduction of costs. The choice of sources basically depends on the required reaction conditions; for instance, bacterial b-galactosidases work with optimal pH between 2.5 and 5.4 and are mainly used for acidic whey hydrolysis. In contrast, yeast b-galactosidase shows maximum activity at pH 6.0–7.0 which is more suitable for the hydrolysis of milk and sweet whey. Sources of b-galactosidases b-Galactosidase is found in bacteria, fungi, and yeasts. In plants, it is mainly found in almonds, peaches, apples, and apricots. However, on a commercial and an industrial scale, the most commonly used sources of b-galactosidase are Aspergillus and Kluyveromyces (Zhou and Chen 2001). 123 3 Biotech (2017) 7:79 Bacterial sources b-Galactosidase extracted from bacterial sources has been used for lactose hydrolysis due to several advantages including their high activity, ease of fermentation, and the stability of the enzyme. b-Galactosidase obtained from Bifidobacterium (a probiotic organism) is utilized in food and food systems. b-Galactosidase from various bacterial strains like Bifidobacterium infantis strain CCRC 14633, Bifidobacterium longum strain CCRC 15708 and Bifidobacterium longum CCRC15708 has shown highest enzyme activity (Hsu et al. 2005). Lactobacillus and Bifidobacterium species are effective probiotics, and hence. they are widely used as potential sources of b-galactosidase. Lactobacilli isolated from piglet’s gastrointestinal tract (GIT) are also used in the production of various fermented milk products. Moreover, b-galactosidase derived from the porcine strains of Lactobacilli has the ability to ferment lactose in (...truncated)