Polyols are naturally produced by a range of microbes, as chemically active compounds that serve as intra- and extracellular osmolytes. These compounds aid the cell in osmotically stressful environments. Besides being osmolytes, the sugar alcohols also serve, like fatty acids, as a way of storing excess carbon, and as such they are produced in the growth phase, where excess carbon is available, i.e. the exponential growth phase.
In this study, an exploratory approach is taken to elucidate the productivity of polyols and other industrially relevant compounds, when Y. lipolytica is grown on glycerol under various cultivation conditions.
Our experimental data shows that during growth on glycerol in minimal media, the production of sugar alcohols is closely coupled to the availability of carbon. The excess carbon is converted to sugar alcohols and secreted to the extracellular medium. These are then consumed when the primary carbon source is depleted. The data shows that mannitol is by far the most abundant polyol and product in the medium. When grown in a pH range from acidic to neutral the data shows that the concentration of secreted products increases significantly, whereas the difference in cellular size decreases as the pH approaches neutral pH from acidic pH.