Growth Enhancement of Dunaliella salina by Microbubble Induced Airlift Loop Bioreactor (ALB)—The Relation between Mass Transfer and Growth Rate

Kezhen Ying,William B. Zimmerman,Yuzhen Shi,Daniel J. Gilmour

doi:10.4236/jbnb.2013.42a001

Abstract

The efficiency of a novel microalgal culture system (an airlift loop bioreactor [ALB] engaged with a fluidic oscillator to produce microbubbles) is compared with both a conventional ALB (producing fine bubbles without the fluidic oscillator) and non-aerated flask culture. The impact of CO2 mass transfer on Dunaliella salina growth is assessed, through varying the gas (5% CO2, 95% N2) dosing flow rate. The results showed that approximately 6 - 8 times higher chlorophyll content was achieved in the aerated ALB cultures than in the non-aerated flasks, and there was a 20% - 40% increase in specific growth rate of D. salina in the novel ALB with microbubbles when compared with the conventional ALB cultures. The increase in chlorophyll content was found to be proportional to the total amount of CO2 mass transfer. For the same dosing time and flow rate, higher CO2 mass transfer rate (microbubble dosing) resulted in a greater growth rate.

Highlights

Microalgae have been considered for CO2 capture from flue gas by many industries recently, due to their high CO2 uptake efficiencies which are one order of magnitude (10 to 50 times) higher than those of terrestrial plants [1]
The results showed that approximately 6 - 8 times higher chlorophyll content was achieved in the aerated Airlift Loop Bioreactor (ALB) cultures than in the non-aerated flasks, and there was a 20% - 40% increase in specific growth rate of D. salina in the novel ALB with microbubbles when compared with the conventional ALB cultures
The D. salina cells cultured in ALB, either with or without fluidic oscillator engaged, were growing faster compared with the flask culture

Summary

Introduction

Microalgae have been considered for CO2 capture from flue gas by many industries recently, due to their high CO2 uptake efficiencies which are one order of magnitude (10 to 50 times) higher than those of terrestrial plants [1]. Industry is one of the major CO2 producers and fossil fuel consumers, responsible for more than 7% of total world CO2 emissions [2], while the flue gas produced, containing various percentages of CO2, can provide a carbon-rich source for microalgae cultivation. Microalgae capture CO2 for their growth, saving the costs of adding CO2 scrubbing systems [3]. Some microalgae species show a good tolerance to NOx/SOx, and can even capture them as nutrients for growth [4,5]. These high value commercial products can be expected to offset the capital and operating costs

Methods

Results

Conclusion