Impact of Microalgae-Bacteria Interactions on the Production of Algal Biomass and Associated Compounds

Abstract

A greater insight on the control of the interactions between microalgae and other microorganisms, particularly bacteria, should be useful for enhancing the efficiency of microalgal biomass production and associated valuable compounds. Little attention has been paid to the controlled utilization of microalgae-bacteria consortia. However, the studies of microalgal-bacterial interactions have revealed a significant impact of the mutualistic or parasitic relationships on algal growth. The algal growth, for instance, has been shown to be enhanced by growth promoting factors produced by bacteria, such as indole-3-acetic acid. Vitamin B12 produced by bacteria in algal cultures and bacterial siderophores are also known to be involved in promoting faster microalgal growth. More interestingly, enhancement in the intracellular levels of carbohydrates, lipids and pigments of microalgae coupled with algal growth stimulation has also been reported. In this sense, massive algal production might occur in the presence of bacteria, and microalgae-bacteria interactions can be beneficial to the massive production of microalgae and algal products. This manuscript reviews the recent knowledge on the impact of the microalgae-bacteria interactions on the production of microalgae and accumulation of valuable compounds, with an emphasis on algal species having application in aquaculture.

Keywords: aquaculture; microalgae; microalgae production; microalgae-bacteria interactions.

Figure 1

Interaction between microalgae and bacteria. Some of the main chemical mediators (A,B) and potential applications. Micronutrients like vitamins and macronutrients like nitrogen, oxygen and carbon usually exchange between algae and bacteria (Improvement in biomass productivity and quality). Photosynthetic oxygen can be consumed by bacteria creating a suitable environment for algal hydrogen production (energy production). A typical example of mutualism is that the bacteria supply vitamin B₁₂ (depicted by molecule B in the Figure) to the algae in exchange for fixed carbon (depicted by molecule A in the Figure). Antibiotics can be produced by the bacteria for algal protection against other microorganisms (mutualism/commensalism) or for algal lysis (parasitism, control of algal blooms). AHL (acyl-homoserine lactone) is produced by bacteria and is involved in biofilm formation between bacteria and algae cells (wastewater treatment and biomass harvesting improvement).