V: Anaerobic treatment (incubation in a 20-l plastic chamber at 20 ℃, with first a rapid atmosphere
exchange by ventilation with humidified nitrogen at a flow rate of 100 ml/min for 2 h, and then a
continuous influx of humidified nitrogen at 50 ml/min-flow rate for 3 d) ANA3d(Polenta et al., 2006).