Screening for the Heterotrophic Cultivation of Chlorella sorokiniana Using an Indirect Impedance Microbiological Technique

Abstract

Heterotrophic culturing of microalgae is of great interest as it has the potential to produce feedstock for added-value bioproducts. The general expectation is to develop a method that can help screen for different media compositions and batch fermentation settings more easily and faster. In the current study, an indirect impedance microbiological technique was used to test the effects of various carbon and nitrogen sources on the growth of Chlorella sorokiniana. It was found that this technique has great potential to screen for heterotrophic cultivation conditions of microalgae as the metabolic rate of microorganisms can be determined by measuring the amount of CO₂ produced. The BacTrac 4100^® was proven to be a suitable instrument to compare several different small-scale culturing settings. Considering the relative changes in impedance observed, the initial cell cumber exhibits an inverse linear correlation with the detection time. Chlorella sorokiniana exhibited an enhanced degree of growth on yeast extract and tryptone, and preferred glucose over acetate or glycerol. An optimum rate of growth at a glucose concentration of 20 gL^-1 was also determined. Our novel approach in the field of heterotrophic cultivation of microalgae envisages great prospects for the method in terms of the design of experiments in the field of media optimization.