Experimental Materials

• XO: 0.2% xylenol orange disodium water solution diluted 30 times for usage.
• Glucose, fructose, galactose, maltose, sucrose and lactose: 8 mmol/L water solution.
• The solution used to dilute bacteria: 0.9 % NaCl water solution (normal saline)
• Co²⁺: 1.5 mmol/L CoCl2 water solution.

Experimental Steps

1. Amplify the bacteria in Luria-Bertani (LB) culture at 37 °C for 12 h. After that, collect the cultured bacteria by centrifugation (5000 rpm, 5 min). Then dilute the bacteria to OD600 = 0.6.
2. Mix the diluted bacteria with the 6 kinds of sugar solution in the ratio of 1:1 for 6h in 37℃ closed environment.
3. Centrifugate the mixed solution in the condition (6000 rpm for 5min) and collect the supernatant. Then, mix the XO indicator, supernatant, and Co²⁺ in the ratio of 1:1:1.
4. Add 200μL of the 6 kinds of mixture to the 96-well plate, and measure absorbance at 580nm. Then, input the results according to each sugar.

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