Bacterial intervention on the growth, nutrient removal and lipid production of filamentous oleaginous microalgae Tribonema sp.

Abstract The present study explores the effects of three bacteria, namely Rhizobium rosettiformans, Hydrogenophaga intermedia, Sphingopyxis terrae and their mix culture on the growth, pigment content, nutrient removal, lipid content and fatty acid composition of microalgae Tribonema sp. S. terrae and mix culture did not affect the biomass of Tribonema sp. noticeably while H. intermedia and R. rosettiformans significantly reduce the biomass. The removal rate of total phosphorous (TP) and total nitrogen (TN) were boosted to 98.34% and 94.64% by addition of S. terrae and Tribonema sp., respectively compared to control (90.13% and 86.20%, respectively). Moreover, S. terrae improved the chlorophyll b content significantly in Tribonema sp. to 1.17 mg/g by 18% higher than the control group. Addition of S. terrae and R. rosettiformans increased the lipid content of Tribonema sp. by 21% and 13%, respectively compared to the control. Regarding fatty acid (FA) profile and biodiesel properties, co-culture of S. terrae with Tribonema sp. showed high contents of unsaturated fatty acid (USFA) and C16-C18 FA, plus low saturated fatty acid (SFA) and polyunsaturated fatty acid (PUFA) contents that are preferable for excellent biodiesel performance. Hence, the S. terrae intervention has the most significant effect on nutrients removal, pigment content, lipid content and biodiesel quality.