Optimization of the associative growth of novel yoghurt cultures in the production of biomass, β-galactosidase and lactic acid using response surface methodology

Abstract

a b s t r a c tThe associative growth of Streptococcus thermophilus 95/2 (St 95/2) and Lactobacillus delbrueckii ssp. bulgaricus 77 (Lb 77) isolated from the Toros mountain region of Turkey was investigated with respect to lactic acid, biomass and b-galactosidase enzyme production using response surface methodology (RSM).The ratio (St 95/2:Lb 77) of the strains and media formulation had significant effect on all responses (p < 0.001). The predicted enzyme activity (2.14 U mL À1 ), lactic acid (22.50 g L À1 ) and biomass (7.11 g L À1 )production at optimum conditions were very close to the actual experimental values (2.14 U mL , respectively). The optimum conditions were to use these cultures in a ratio of 1.66:1.62 (St 95/2:Lb 77) in a medium containing whey (5%), corn steep liquor (4%), potassium phosphate (2%) and peptone (2%) at 43 C for 8 h. The associative growth provided 6.4% and 39% more b-galactosidase activity and 8.73% and 44% more lactic acid compared with the results obtained using pure St 95/2 and Lb 77 strains, respectively.

Biochemical and thermal properties of β-galactosidase enzymes produced by artisanal yoghurt cultures

“…Another objective of the study was to compare the enzymes produced from pure cultures as opposed to mixed cultures. In fact, in our previous study (Tari, Ustok & Harsa, 2009), we determined that the associative growth of the two strains in the same fermentation medium increased the enzyme yield significantly. Therefore, it is highly important to compare the properties of this enzyme (produced under associative growth conditions) with those produced by pure strains.…”

“…bulgaricus 77 (Lb 77) strains, were determined to be potential b-galactosidase enzyme producers (Tari, Ustok & Harsa, 2009). These enzymes were characterised in view of the fact that enzymes from new sources may exhibit different properties and possible novelties.…”

The effects of nutrient supplements on the production of lactic acid from cheese whey

“…Another alternative is the production of lactic acid from whey permeates by fermentation with lactic acid bacteria [15]. Lactase (β-galactosidase, β-D-galactoside, galactohydrolase, EC 3.2.1.23) an enzyme occurs in lactic acid bacteria that hydrolyzes lactose to glucose and galactose [16,17]. Nutrient supplements such as yeast extract, corn steep liquor and lactamine AA can improve the nutritional quality of the medium, because they contain, all essential amino acids growth promoting compounds, in addition to organic nitrogen, and carbonaceous compounds.…”

Immobilized Lactobacillus acidophilus produced from whey and alginate

“…The experimental results revealed an optimized viable cell concentration of about 10 10 MPN/mL and cell concentrations of 6.0 ± 0.7 g/L. The cell concentration was about 1.38-fold higher than that reported in the literature (Tari et al, 2009). …”