Microalgae growth rate

Figure 3. Relative growth rate of polysaccharide-producing microalgae...

The synthesis of microbial fat by bacteria is often ignored because the average fat concentration in dry biomass does not exceed 10%. However, there are strains of Arthrobacter sp., Mycobacterium, and Corynebacterium that are able to accumulate from 30 to 80% lipids in dry matter. Unfortunately, there are other problems related to low growth rates and yields of bacteria, lipid extraction, and the possible allergeiucity and toxicity of the resulting lipids. Microalgae (e.g., Botryococcus braunii and Chlorella pyrenoidosa) serve as attractive sources of PEFA. Dry biomass fat can amount to as much as 85% (Kay, 1991). Moreover, microalgae are a very... 

Maximum specific growth rate rx,max h meant as a state, where no external substrate is limiting, but a—in most cases not known— intracellular step. The metabolism of the cell consists of physical and enzymatically catalyzed steps, which may differently react to different temperatures. Especially for microalgae, the photosynthetic apparatus down to proton transport through the thylakoid membrane as a transport step could react differently from the anabolic reactions. Explanations and first model approaches for combined temperature/Hght effects are given in Bechet et al (2013), Bernard and Remond (2012), and Yun and Park (2003). 

A simple substrate balance according to Pitt (1965) can be used to couple the specific consumption rate of sugar outside of the chloroplast to the specific growth rate of the microalgae... 

Because the specific growth rate fi of microalgae is directly related to the rate of photosynthesis qs, also the specific growth rate is affected by the acclimation state of the microalgae. It might seem very strange that there are multiple relations between specific growth rate and photon flux density a different one for every possible value of the specific absorption coefficient... 

Figure 17 Instantaneous specific growth rate fipi of a microalga as a function of photon flux density /ph and the influence of photoacclimation. The specific growth rate is derived from a substrate balance according to Pirt in combination with the photosynthesis models of Jassby and Platt. Parameter values based on Chlorella sorokiniana ax=3.5 m moix (high light) Ox=7.0 m moix (low light) ...

With respect to the design and operation of photobioreactors the production term tx is of major importance. Parameter represents the volumetric biomass production rate of a cultivation system and it is the product of the biomass concentration in the system and the average specific growth rate of the microalgae ... 

In order to assess the volumetric productivity of the system the micro-algal biomass concentration and average specific growth rate need to be known. For the moment it will be assumed that the biomass concentration can be set at any desired level by means of a turbidostat mode of operation. Consequently, only the average specific growth rate of the microalgae in the photobioreactor needs to be calculated. 

Barbosa MJ, Janssen M, Ham N, et al Microalgae cultivation in air-lift reactors modeling biomass yield and growth rate as a function of mixing frequency, Biotechnol Bioeng... 

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