Growth characterization and biomass quantification strategies of the marine microalgae Nannochloropsis gaditana and Tetraselmis chuii

Abstract

Microalgae are phototrophic microorganisms that have been studied and commercially grown for food, biofuel and pharmaceutical/nutraceutical purposes. Many of these microalgae species inhabit the sea and/or brackish and saline waters. As the availability of freshwater is becoming increasingly scarce both in the UAE and worldwide, marine microalgae represent an opportunity to grow a sustainable protein source for food, feed, chemicals and fuels without the use of freshwater resources. In this thesis, two marine microalgae species Nannochloropsis gaditana and Tetraselmis chuii are subjected to sequential batch reactor operations (8 cycles for N. gaditana and 6 cycles for T. chuii) to determine their maximum growth rates, along with a rapid method of Optical Density at three key wavelengths (550 nm, 680 nm and 740 nm) was developed to correlate to biomass measured as Volatile Suspended Solids The maximum specific growth rate of growth achieved by N. gaditana was 0.23 ± 0.01 d -1 whereas T. chuii achieved a higher observed maximum specific growth rate of 0.3 d -1 . Then, another set of experiments are performed to determine the nitrate uptake rates and the effects of nitrate concentration on their rate of growth were determined for the two species. Maximum specific nitrate uptake rates were found to be 210 and 840 gNO3.gVSS-1 .d-1 for N. gaditana and T. chuii respectively. Moreover, it was found that the biomass growth rate was not dependent on extracellular nitrate concentration as depicted by the Monod growth model as there appeared to be a decoupling between nutrient uptake and growth. All these empirically derived parameters are investigated for the purpose of modelling the growth of these two species.

Date of Award	Jul 2018
Original language	American English
Supervisor	Jorge Rodriguez (Supervisor)