Simultaneous control of turbidity and dilution rate through adjustment of medium composition in semi‐continuous Chlamydomonas cultures

Abstract

For production of starch in algal cultures, a growth rate limited by a nutrient is an important factor. Under phototrophic conditions, turbidity must be also paid attention, as the shading effect may affect its productivity. Semi-continuous cultivation methods, which enable control of turbidity and dilution rate (D) at the same time, have been developed for evaluation of those factors on starch production in Chlamydomonas sp. A specific feature of the methods is in a process of alternately feeding medium adjusted at two different nitrogen (N) concentrations. In the turbidostat-based method, a turbidostat culture was operated repeating three steps of determining D within a preset interval, alternating media by comparing the D with a preset value, and adjusting D in the next interval by feeding the selected medium. In the chemostat-based method, turbidity of a chemostat culture was controlled by repeating two steps of alternating media by comparing transmitted photon flux intensity (I) with a preset value and adjusting I by feeding the selected medium. D controlled by the turbidostat-based method reached quickly a preset value as low as 0.010/h, and then it was dispersed around but above the preset value. On the other hand, mean N concentrations of fed media formed a plateau. In the chemostat-based method, I was well controlled to a preset value while the mean N concentrations were a bit fluctuated. Starch concentration varied from 0.052 to 0.41 g/L with turbidity and D defined by these methods.

Microalgae—novel highly efficient starch producers

“…Nitrogen limitation is often used for increasing production of starch (Eriksen et al, 2007;Maeda et al, 2006;Rodolfi et al, 2009). A disadvantage of nitrogen or phosphorus limitation is that while the cells succeeded in increasing starch content before dying, their viability decreased within a relatively short time interval due to effects on cell metabolism (Fig.…”

Continuous cultivation of photosynthetic microorganisms: Approaches, applications and future trends

“…Besides nutrient concentration, also the influence of salt adaptation, light quality and quantity, initial biomass concentration, turbidity, temperature, culture age, and dilution rate have been studied using continuous cultivation mode (Alonso et al, 2000;Blumwald and Tel-or, 1984;Camacho et al, 1990;Carvalho and Malcata, 2005;Imaizumi et al, 2014;Lamers et al, 2010;Madhyastha and Vatsala, 2007;Maeda et al, 2006;San Pedro et al, 2013;Sassano et al, 2007;Sassano et al, 2010;Sobczuk and Chisti, 2010;Utkilen and Gjølme, 1992). Blumwald and Tel-or (1984) tested the influence of the salt-adaptation phenomenon in the physiological state of the cyanobacterium Synechococcus 6311.…”

Photobioreactors in Life Support Systems

“…Starch production of Chlamydomonas sp. was studied in continuous cultures by Maeda et al [21], whereas Lamers et al [22] investigated carotenoid and fatty acid metabolism dependent on a light regime in turbidostat cultures of the halophile green alga Dunaliella salina. In general, for continuous microalgae cultures no manual maintenance is required; a complete automated cultivation can be conducted by pure process engineering.…”

“…In contrast to filamentous cyanobacteria such as Arthrospira plantensis most species of eukaryotic microalgae are unicellular and suspension cultures as well as immobilized cultures can be realized. Microalgae can be grown easily, also in continuous cultures [20][21][22]. Starch production of Chlamydomonas sp.…”