A structured model for simulation of cultures of the cyanobacterium Spirulina platensis in photobioreactors: II. Identification of kinetic parameters under light and mineral limitations

Abstract

A structured model for the culture of cyanobacteria in photobioreactors is developed on the basis of Schuster's approximations for radiative light transfer. This model is therefore limited to monodimensional geometries and kinetic aspects.Light-harvesting pigments play a crucial role in defining the profile of radiative transfer inside the culture medium and in controlling the metabolism, particularly the metabolic deviations induced by mineral limitations. Modeling therefore requires the biomass to be divided into several compartments, among which the light-harvesting compartment allows a working illuminated volume to be defined within the photobioreactor. This volume may change during batch cultures, largely decreasing as pigment concentration increases during growth but increasing as pigments are consumed during mineral limitation. This approach enables, in photobioreactors of simple parallelepipedic, geometries, kinetic parameters to be determined with high accuracy; this may then be extended to vessels of more complex geometries, such as cylindrical photobioreactors.The model is applied to controlled batch cultures of the cyanobacterium Spirulina platensis in parallelepipedic photobioreactors to assess its ability to predict the behavior of these microorganisms in conditions of light and mineral limitations. Results allowed the study of optimal operating condition for continuous cultures to be approached.

Arthrospira (Spirulina) platensis cultivation in tubular photobioreactor: Use of no-cost CO2 from ethanol fermentation

“…In fact, the N/P ratio in the nutrients solution added during the cultivation (2.99) was by far lower than that of dry A. platensis biomass (12.8), which can estimated from the elemental composition reported for this microorganism by Cornet et al [36] (CH 1.650 O 0.531 N 0.170 S 0.007 P 0.006 ). Finally these results suggest that, under bioenergetic stress conditions, i.e.…”

“…The total carbonate concentration (about 9.0 g L À1 ) kept almost constant during all the runs, thus suggesting that the CO 2 addition was able to replace the consumed carbon source, avoiding, at the same time, any accumulation in the medium. Taking as an example the run 1 (Table 1), whose P X value was 0.444 g L À1 d À1 and considering that the dry cell weight is constituted by about 50% of carbon [36], we can estimate a carbon dioxide necessity of 2.849 g/day for the 3.5 L of culture. Taking into account that cells achieved their maximum concentration within 9 days, the total amount of CO 2 required for their growth was about 26 g, which accounts for approximately 84% of the total carbon dioxide present in the initial Schlösser medium (30.8 g), either in the form of bicarbonate or carbonate.…”

Estudo da intensidade luminosa no cultivo de Arthrospira (Spirulina) platensis em reator tubular utilizando sulfato de amônio como fonte de nitrogênio por processo descontínuo alimentado

“…platensis, e os melhores resultados são atribuídos aos nitratos em termos de biomassa produzida (FAINTUCH, 1989;CORNET et al, 1998), o que confirma a ampla utilização dos meios de Paoletti (PAOLETTI et al, 1975) e Zarrouk (ZARROUK, 1966), que utilizam KNO 3 e NaNO 3 como fonte de nitrogênio, respectivamente.…”

Influência do tempo de alimentação e da intensidade luminosa no cultivo de 'Spirulina platensis' sob alimentação com cloreto de amônio

“…Ficocianinas são cromoproteínas que constituem o principal pigmento na captação de luz em cianobactérias e representa 1/2 das proteínas celulares. Na falta de nitrogênio e enxofre, essas cromoproteínas são consumidas reduzindo a eficiência fotossintética (CORNET et al, 1992).…”

“…Com a adição da fonte de nitrogênio em cultivos deficientes em nitrogênio, ocorre um rápido aumento na quantidade de proteínas, tais como ficocianinas e, com menos intensidade, outras proteínas celulares são produzidas (CORNET et al, 1998 O pH também influencia na disponibilidade de nitrogênio para a célula, visto que com pH abaixo de 8,0 há uma predominância de íon amônio. Em pH acima de 11,0, o nitrogênio encontra-se na forma não protonada de amônia que é a forma que tem passagem livre pela membrana celular (BOUSSIBA, 1989;BELKIN & BOUSSIBA, 1991 (MORIST et al, 2001).…”