*5.4.1 Influence of glucidic compounds*

Inoculum M9 at different glucidic concentrations has been tested (**Table 2**). Notably: 1 liter at 1% glucose and 0.05% glucose respectively, and 1 liter at 1% saccharose and 0.05% saccharose respectively. These substrates have been selected in light of their ease to be metabolized so that fast results were expected to be attained with respect to the work objectives. The four substrates, after sterilization at 5% inoculum, have been put in a 1.5 liter flask equipped with two air-in / air-out capillaries for sterile air blowing. Each flask has been equipped with a 2 cm2 Petri dish, adopted as attachment surfaces. The culture has been conducted under hood for 24 hours at ambient temperature of around 25°C. Suspended bacteria growth rates have been measured during this time, by means of spectrophotometric readings at 600 nm, and utilizing, as reference, the relevant blank substrates. During this phase, visual checks have been made as to the clarification degree and foam formation for all cases, and dissolved oxygen has been measured. After 24 hours, fragments of Petri dishes have been collected, gently washed with deionized water and attached microorganism have been stabilized on the solid support by using a Bowin fixative (**Table 3**). Afterwards, the fragments have been dried under laminar hood for 24 hours and fixative removal has been accomplished by means a 50% ethanol solution, and Crystal violet Hucker's solution has been used for attached cells colouration (**Table 4**). Microscopic observations have allowed for a qualitative-quantitative evaluation of the attached biomass.
