Capillary zone electrophoresis for enumeration of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in yogurt

Journal article

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WORAPOT SUNTORNSUK

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Publication Details

Author list: Lim O., Suntornsuk W., Suntornsuk L.

Publisher: Elsevier

Publication year: 2009

Journal: Journal of Chromatography B (1570-0232)

Volume number: 877

Issue number: #

Start page: 710

End page: 718

Number of pages: 9

ISSN: 1570-0232

URL: https://www.scopus.com/inward/record.uri?eid=2-s2.0-61349107385&doi=10.1016%2fj.jchromb.2009.02.014&partnerID=40&md5=0f556a188101f1802c30bbef3220e7b0

Languages: English-Great Britain (EN-GB)

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Abstract

Enumeration of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus is a priority due to their importance in yogurt production. Capillary electrophoresis (CE) of both bacteria could be achieved in 7.2 min with a resolution of 3.2 in the background electrolyte (BGE) containing 4.5 mM Tris(hydroxymethyl) amminomethane (TRIS)-4.5 mM boric acid-0.1 mM ethylenediamine tetraacetate (EDTA) (TBE) buffer (pH 8.4) and 0.05% (v/v) polyethylene oxide (PEO), using a capillary of 47.5 cm (effective length) × 100 μm i.d., injection of 50 mbar × 3 s followed by -5 kV × 120 s, a voltage and temperature of 20 kV and 25 °C, respectively. Appropriate amounts of PEO in the BGE, sample preparation (i.e. vortex) and introduction were key factors for their separation. A short hydrodynamic injection followed by applying reversed polarity voltage could compress the bacteria into narrow zones, which were detected as separated single peaks. Method linearity (r2 > 0.99), precision (%RSDs < 9.3%), recovery (%R = 91.7-106.7%) and limit of quantitation (1.0 × 106 colony forming unit per mL (CFU/mL)) were satisfactory. Results from the CE analysis of both bacteria in yogurt were not statistically different from those of the plate count method (P > 0.05). The CE method can be used as an alternative for quantitation of L. delbrueckii subsp. bulgaricus and S. thermophilus in yogurt since it was reliable, simple, cost and labor effective and rapid, allowing the analysis of 3 samples/h (comparing to 2d/sample by plate count method). © 2009.

Keywords

Capillary zone electrophoresis, Lactobacillus delbrueckii subsp bulgaricus, Streptococcus thermophilus, Yogurt