Effects of pH, Temperature, Supplementation with Whey Protein Concentrate, and Adjunct Cultures on the Production of Exopolysaccharides by Streptococcus thermophilus 1275

Abstract

Effects of pH, temperature, supplementation with whey protein concentrate (WPC), and non-EPS culture on the exopolysaccharide (EPS) production by Streptococcus thermophilus 1275 were studied. The organism was grown in 10% reconstituted skim milk (RSM) in a Biostat B fermenter for 24 h at various pH (4.5, 5.5 and 6.5) and temperatures (30, 37, 40, and 42 degrees C), and supplementation with WPC 392, and non-EPS producing S. thermophilus 1303 and the amount of EPS produced were determined. Bacterial counts were enumerated and the concentrations of lactic acid, lactose, glucose, and galactose were also determined. A maximum of 406 mg/L of EPS was produced in RSM at 37 degrees C after 24 h of fermentation at pH 4.08 when the pH was not controlled. A pH of 5.5 and temperature of 40 degrees C were found to be optimal for EPS production by S. thermophilus 1275, yielding 458 mg/L. The EPS production increased when RSM was supplemented with WPC 392. At optimum pH and at 37 degrees C with WPC supplementation, the level of EPS increased to 1029 mg/L. Co-culturing S. thermophilus 1275 with non-EPS S. thermophilus 1303 increased EPS production at 37 degrees C and pH 5.5 to 832 mg/L. High temperature (42 degrees C) reduced the amount of EPS production, and EPS production ceased at pH 4.5 when maintained constantly at this pH. The level of lactose utilization and lactic acid production depended on growth conditions of the organism. No glucose was detected, while galactose was found to accumulate in the medium.

Inducible Gene Expression in Lactobacillus reuteri LTH5531 during Type II Sourdough Fermentation

“…Up to now, no results have been published investigating the regulation of L. reuteri genes involved in EPS production. However, EPS production has been shown to be affected by environmental factors, like temperature and pH, e.g., in Lactobacillus helveticus ATCC 15807 (40,41) and Streptococcus thermophilus 1275 (46). Therefore, it is tempting to speculate that L. reuteri LTH5531 may synthesize EPS in sourdough under control of the transcriptional regulator that we have detected.…”

Survey of selected chemical and microbiological characteristics of (plain or sweetened) natural yoghurts from the Italian market

“…Although these polysaccharides mainly consist of galactose and glucose [4], their composition can be largely affected by availability of different carbon sources [8,15,16]. Moreover, Zisu and Shah [42] reported ST 1275 to produce a maximum of 20 mg EPS per 100 mL after 12 h of incubation at 37°C in reconstituted skimmed milk without pH adjustment. Taking into account this feature, the adopted procedure particularly intended for thickener extraction could not be selective for a low level of EPS.…”

Effect of inulin and oligofructose on the physicochemical, microbiological and sensory characteristics of symbiotic dairy beverages

“…The control formulation (C) showed no significant reduction in pH (p> 0.05). However, there was a significant increase in the acidity values for the control sample, which was probably due to the presence of Streptococcus thermophilus that produces lactic acid and small concentrations of CO 2 and formic acid from the fermentation of lactose resulting in increased acidity (FOX et al, 2000;ZISU;SHAH, 2003). According to Fox and McSweeney (1998), an important characteristic of milk is its high buffering capacity, which is a resistance to change in pH after addition of an acid or base.…”