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. 2016 Apr 11;(110):53249. doi: 10.3791/53249
Main step / Analytical module Workflow Observation / Description
Cultivation of the strains 1 ml EPS-mediuma Pre-culture 48 hr, 30 °C, 1,000 rpma Main-culture 48 hr, 30 °C, 1,000 rpma Production of EPS
Cell removal / viscosity Centrifugation: 30 min at 4,300 x g No pellet = increased viscosity = positive
Detection of Polymer: Precipitation 50 µl supernatant + 150 µl 2-propanolb Shaking 10 min at RT and 900 rpmb Visual: Fibers and flakes = positive precipitation of polymer
Cell removal / high viscosity 180 µl supernatant of main-culture Centrifugation: 10 min at 3,000 x g 1.0 µm glass fiber membrane No filter passing = high viscosity = positive
Detection of Polymer: Precipitation 50 µl filtrate + 150 µl 2-propanolb Shaking 10 min at RT and 900 rpmb Visual: Fibers and flakes = positive precipitation of polymer
Glucose consumption: Glucose-assay Dilution 1:100: 10 µl filtrate + 990 µl ddH2O 50 µl aliquot + 50 µl reagent-mix Incubation 30 min at 30 °C 150 rpm Measurement 418-480 nm Remaining glucose after cultivation
Gel-filtration Equilibration: 3 x 150 µl NH4-acetat buffer pH 5.6 2 x 2 min at 2,000 x g 1 x 2 min at 1,000 x g Gel-filtration: 35 µl filtrate, 2 min at 1,000 x g Washing: 3 x 150 µl ddH2O, 2 min at 2,000 x g 75 µl 20% ethanol for storage Polymer purification: Removal of salts, pyruvate, glucose and other sugar monomers from cultivation supernatant
Remaining glucose after gel-filtration Glucose-assay Dilution 1:10: 25 µl ddH2O +  20 µl ddH2O and 5 µl filtrate + 50 µl reagent-mix Incubation 30 min at 30 °C, 150 rpm Measurement 418-480 nm Subtraction of remaining glucose after gel-filtration from the phenol-sulfuric-acid method
Glucose equivalent:  Phenol-sulfuric-acid methodc 20 µl gel-filtrate + 180 µl phenol-sulfuric-acid (30 µl 5% (w/v) phenol in ddH2O + 150 µl conc. H2SO4 (ρ = 1.84 g/ml)) Shaking 5 min at 900 rpm Incubation 35 min at 80 °C Measurement at 480 nm Glucose equivalent: Δ (phenol-sulfuric-acid value - remaining glucose after gel-filtration) <300 mg/L negative >300 and <700 mg/L putative positive >700 mg/L positive
a Handled manually under sterile conditions (laminar flow).
b Flammable liquid handled manually under a fume hood.
c Phenol-sulfuric-acid handled with Brand Liquid Handling Station (LHS) under a fume hood.