The Effect of Epiphytic Bacteria on Ulva Mutabilis Sugar Content

Macroalgae are a potential feedstock for a sustainable biorefinery since they don’t compete for arable land or potable water. Ulva sp. is particularly interesting due to high growth rates, easy harvest and high carbohydrates content, up to 35-40%. Ulva sp. is a potential source for food and also for products such as monosaccharides, biofuels and bioplastic. The macroalgae cultivation is the first step of the production process before it harvested and processed.

It was discovered recently that specific epiphytic bacteria play a fundamental role in Ulva development. In particular, the bacteria Maribacter sp. strain MS6 and Roseovarius strain MS2 can restore the complete morphogenesis of Ulva mutabilis. This work has shown firstly the difference in sugar content between axenic and non-axenic Ulva biomass.

The U. mutabilis biomass was cultivated with MS6 and MS2 bacteria; as a control we used U. mutabilis bacteria free (axenic) cultures. Then the algae were hydrolyzed into the monomers rhamnose, glucose, xylose, fructose, glucuronic acid and glycerol.

Significant differences between the axenic and the consortium culture were detected in the following compounds: 11.5±2.18% glucose, 3.47±0.65% xylose and 3.45±0.63% glucuronic acid from dry weight detected at the consortium, while 6.5±1.39% glucose, 5.54±0.73% xylose and 6.67±0.69% glucuronic acid at the axenic culture. The current results could be explained by the bacterial impact on the cell wall development or could raise the hypothesis that bacteria causes the algae to accumulate the sugar more in the intercellular area than in the cell wall.

These types of results could lead to a better understanding of the bacterial role in the macroalgae biomass formation, which is critical for developing an efficient biorefinery based on macroalgae.