Volatile organic compounds involved in the communication of microalgae-bacterial association extracted through Headspace-Solid phase microextraction and confirmed using gas chromatography-mass spectrophotometry.

In the present study, bacterial mixture (Rhizobium and Agrobacterium) and axenic Chlorella were cultivated
individually, in a mixed (co-cultured) form, and through headspace connections to study volatile organic compounds
(VOCs) profile and their effect on growth. Results indicated that VOCs produced by the axenic microalgae
and microalgae co-cultured with bacteria were significantly different. Axenic Chlorella predominantly produced a
flavouring organic compound 2-pentadecanone (69.54%), bacterial mixed culture produced 1-decanone, 1,2,3-
butanetriol, and quinoline (15–20%), and direct co-culturing of Chlorella with bacteria predominantly produced
2-pentadecanone (32.4 %). When they were allowed to communicate distantly through headspace connection,
highly diversified VOCs in large numbers but low quantities were noted, predominantly 1,2-propanediol (28.82
%). In addition, growth of the co-cultured Chlorella was 1.5 times higher, while Chlorella in headspace connection with bacterial mixture exhibited ~ 3.2 times increase in growth compared to the axenic Chlorella, indicating the
essential role of VOCs in growth and communication.