Novel Bio-regeneration Concept via Using Rich Solution as Nutrition Resource for Microalgae Cultivation: Effect of pH and Feeding Modes

Abstract

Absorption–bioconversion hybrid process has the advantages of capturing CO2 in the form of bicarbonate in the absorber and utilizing bicarbonate as a carbon source for microalgae growth in the photoreactor. It can simultaneously achieve CO2 capture and utilization and avoid energy consumption of rich solvent regeneration in conventional absorption processes. As a promising solvent for hybrid process, NH3 could capture CO2 at low cost and with high efficiency. However, a high concentration of regenerated NH3 in a photoreactor would adversely affect microalgae growth. Previous work indicated that batch-feeding cultivation and pH adjustment might be a promising alternative to reduce NH3 release rate and its inhibition to microalgae. In this work, the influence of batch-feeding interval (i.e., 3, 6, and 9 days) and pH (i.e., 7, 8, and unadjusted) on the performance of absorption–microalgae hybrid system was investigated. The experimental results indicated that pH control has a significant influence on the growth of microalgae (Chlorella sp. L38) and value-added ingredient yield. NH3 escape ratio could be kept at lower than 34% when the pH was controlled at 7. In addition, a shortened batch-feeding interval would be also beneficial to increase the growth of microalgae, with the NH3 escape ratio decreased to 19%. It could be observed that the performance of the absorption–microalgae hybrid system could be intensified by the pH control and batch-feeding interval optimization.

Microalgae as Raw Materials for Aquafeeds: Growth Kinetics and Improvement Strategies of Polyunsaturated Fatty Acids Production

“…Based on this observation, it is assumed that the addition of bicarbonate limited microalgae growth and further studies were recommended to evaluate lower concentrations. In a similar manner, Song et al [ 112 ] also observed not only that the presence of bicarbonate affects the Chlorella L38 growth but also that the alkaline values of culture media (9.5-10) provoke an increase of ammonia release. Therefore, they proceeded to control pH (7-8), achieving an increase of biomass production of 67% and a release rate of ammonia lower than conventional absorption processes (43.1%).…”

“…Several authors have used bicarbonate (HCO 3 − ) as an inorganic carbon source for microalgae to control pH and reduce the loss of CO 2 [ 106 , 110 – 112 ]. In this context, Roa et al [ 111 ] studied a batch culture system for Chlorella sp in the presence of HCO 3 − .…”

CO2-Inorganic Carbon Auto-Buffering System for Efficient Ammonium Reclamation Coupled with Valuable Biomass Production in a Euryhaline Microalga Tetraselmis subcordiformis

“…The removed NH 4 + -N from the medium could have either been assimilated by the microalgae or stripped out of the culture system as NH 3 [26,27]. In order to gain further insight into the efficiency of NH 4 + -N reclamation by the microalgal cultivation systems, the N balance was analyzed to explore the distribution.…”

Enhanced Photosynthesis of Carotenoids in Microalgae Driven by Light-Harvesting Gold Nanoparticles

“…However, significant challenges have remained in obtaining natural carotenoids from biosynthetic pathways, for example, the requirement of considerable arable land for plants and the low efficiency in converting carbon sources into higher value metabolites in microorganisms. 8,9 Therefore, increasing the overall efficiency of solar-to-chemical conversion in biosynthesis would create greater opportunities for the sustainable and economic supply of these natural products.…”

“…Due to the growing demand of customers for natural foods as well as sustainable development, the production of such bioproducts from natural renewable sources has become an emerging and important goal from scientific and industrial aspects. However, significant challenges have remained in obtaining natural carotenoids from biosynthetic pathways, for example, the requirement of considerable arable land for plants and the low efficiency in converting carbon sources into higher value metabolites in microorganisms. , Therefore, increasing the overall efficiency of solar-to-chemical conversion in biosynthesis would create greater opportunities for the sustainable and economic supply of these natural products.…”