Mixotrophic Co-Cultivation of Chlorella lewinii LC172265 and Kluyveromyces marxianus NCYC2791 for Efficient Production of Biomass under Static Condition

Background: Microalgae and yeast biomass are sources of many useful metabolites such as proteins, lipids, antioxidants, vitamins and a host of pharmaceuticals. However, efficient production of microalgae biomass requires constant supply of carbon dioxide and removal of photosynthetically generated oxygen. On the other hand, production of yeast biomass requires adequate supply of organic carbon and constant supply of oxygen. It is therefore expected that co-culture of the two microorganisms can be achieved without aeration since the culture will be oxygenated by the oxygen released by the microalgae and carbon dioxide will be supplied by yeast fermentation.

Aim: In the present study, the feasibility of co-cultivation of Chlorella lewinii and Kluyveromyces marxianus for efficient production of biomass without aeration was investigated.

Methods: BG11 medium was used as the basic medium and the effects of nitrogen source on the growth of the cells in monocultures were first investigated. Subsequently, the effects of inoculum ratios and glucose concentrations on the growth of Chlorella lewinii, Kluyveromyces marxianus and total biomass concentrations in co-cultures were investigated.

Results: The results showed that urea was the best nitrogen source for the growth of the two strains. In their monocultures, the maximum concentrations of C. lewinii and K. marxianus were1.62 x 109cells/ml and 7.719 x108cells/ml, respectively. The optimum inoculum ratio of K. marxianus to C. lewinii was 1:60 and a total cell concentration of 8.25 x109cells /ml was achieved. Although as the initial glucose concentration was increased from 5 g/L to 20 g/L, the total biomass concentration increased, the growth of K. marxianus increased while that of C. levinii decreased. The highest total biomass yield per gram of glucose was obtained with an initial glucose concentration of 5 g/L.

Conclusion: Co-cultures of C. lewinii and K. marxianus is an effective method for production of their biomass without external supply of oxygen and carbon dioxide.