Modeling and optimization of biomass productivity of Chlorella vulgaris using response surface methodology, analysis of variance and machine learning for carbon dioxide capture.

This study explores bioremediation's effectiveness in reducing carbon emissions through the use of microalgae Chlorella vulgaris, known for capturing carbon dioxide and producing biomass. The impact of temperature and light intensity on productivity and carbon dioxide capture was investigated, and cultivation conditions were optimized in a photobioreactor using response surface methodology (RSM), analysis of variance (ANOVA), and deep neural networks (DNN). The optimal conditions determined were 28.74 °C and 225 µmol/m2/s with RSM, and 29.55 °C and 226.77 µmol/m2/s with DNN, closely aligning with literature values (29 °C and 225 µmol/m2/s). DNN demonstrated superior performance compared to RSM, achieving higher accuracy due to its capacity to process larger datasets using epochs and batches. The research serves as a foundation to further in this field by demonstrating the potential of utilizing diverse mathematical models to optimize bioremediation conditions, and offering valuable insights to improve carbon dioxide capture efficiency in microalgae cultivation.

The influence of light intensities and micropollutants on the removal of total coliforms and E. coli from wastewater in a flat-panel photobioreactor.

The presence of micropollutants and pathogens in sanitary wastewater and surface water is a growing concern that impacts public health, environmental balance and the maintenance of water supply services. To improve sanitary wastewater treatment, it is necessary to develop and improve sustainable technologies. Among the available options, microalgae-based systems stand out for their efficiency and generation of value-added byproducts. To study the impact of luminosity and the presence of micropollutants (13 selected) on the removal of E. coli and total coliforms from real anaerobically treated wastewater, a pilot flat-panel photobioreactor (50 L) was operated in batch mode in a tropical climate region. This is the first study to evaluate whether micropollutants interfere with coliform groups, considering a microalgae-based system and an experiment in a tropical climate region. E. coli had better removal (from 104 to 101 CFU 100 mL-1) than did total coliforms (from 104 to 103 CFU 100 mL-1). The removal of E. coli was more strongly linked to luminosity and temperature, while the removal of total coliforms was influenced by the presence of the selected micropollutants.

Pilot composite tubular bioreactor for outdoor photo-fermentation hydrogen production: From batch to continuous operation.

A novel 70 L composite tubular photo-bioreactor was constructed, and its photo-fermentation hydrogen production characteristics of batch and continuous modes were investigated with glucose as the substrate in an outdoor environment. In the batch fermentation stage, the hydrogen production rate peaked at 37.6 mL H2/(L·h) accompanied by a high hydrogen yield of 7 mol H2/mol glucose. The daytime light conversion efficiency is 4 %, with 37 % of light energy from the sun. An optimal hydraulic retention time of 5 d was identified during continuous photo-fermentation. Under this condition, the stability of the cell concentration is maintained and more electrons can be driven to the hydrogen generation pathway while attaining a hydrogen production rate of 20.7 ± 0.9 mL H2/(L·h). The changes of biomass, volatile fatty acids concentration and ion concentration during fermentation were analyzed. Continuous hydrogen production by composite tubular photo-bioreactor offers new ideas for the large-scale deployment of photobiological hydrogen production.

Strategies to enhance biohydrogen production from microalgae: A comprehensive review.

Microalgae represent a promising renewable feedstock for the sustainable production of biohydrogen. Their high growth rates and ability to fix carbon utilizing just sunlight, water, and nutrients make them well-suited for this application. Recent advancements have focused on improving microalgal hydrogen yields and cultivation methods. This review aims to summarize recent developments in microalgal cultivation techniques and genetic engineering strategies for enhanced biohydrogen production. Specific areas of focus include novel microalgal species selection, immobilization methods, integrated hybrid systems, and metabolic engineering. Studies related to microalgal strain selection, cultivation methods, metabolic engineering, and genetic manipulations were compiled and analyzed. Promising microalgal species with high hydrogen production capabilities such as Synechocystis sp., Anabaena variabilis, and Chlamydomonas reinhardtii have been identified. Immobilization techniques like encapsulation in alginate and integration with dark fermentation have led to improved hydrogen yields. Metabolic engineering through modulation of hydrogenase activity and photosynthetic pathways shows potential for enhanced biohydrogen productivity. Considerable progress has been made in developing microalgal systems for biohydrogen. However, challenges around process optimization and scale-up remain. Future work involving metabolic modeling, photobioreactor design, and genetic engineering of electron transfer pathways could help realize the full potential of this renewable technology.

Optimizing cultivation strategies and scaling up for fucoxanthin production using Pavlova sp.

The microalgal-based production of fucoxanthin has emerged as an imperative research endeavor due to its antioxidant, and anticancer properties. In this study, three brown marine microalgae, namely Skeletonema costatum, Chaetoceros gracilis, and Pavlova sp., were screened for fucoxanthin production. All strains displayed promising results, with Pavlova sp. exhibiting the highest fucoxanthin content (27.91 mg/g) and productivity (1.16 mg/L·day). Moreover, the influence of various cultivation parameters, such as culture media, salinity, sodium nitrate concentration, inoculum size, light intensity, and iron concentration, were investigated and optimized, resulting in a maximum fucoxanthin productivity of 7.89 mg/L·day. The investigation was further expanded to large-scale outdoor cultivation using 50 L tubular photobioreactors, illustrating the potential of Pavlova sp. and the cultivation process for future commercialization. The biomass and fucoxanthin productivity for the large-scale cultivation were 70.7 mg/L·day and 4.78 mg/L·day, respectively. Overall, the findings demonstrated considerable opportunities for fucoxanthin synthesis via microalgae cultivation and processing.

Assessment of photosynthetic activity in dense microalgae cultures using oxygen production.

Microalgae are photosynthetic microorganisms playing a pivotal role in primary production in aquatic ecosystems, sustaining the entry of carbon in the biosphere. Microalgae have also been recognized as sustainable source of biomass to complement crops. For this objective they are cultivated in photobioreactors or ponds at high cell density to maximize biomass productivity and lower the cost of downstream processes. Photosynthesis depends on light availability, that is often not constant over time. In nature, sunlight fluctuates over diurnal cycles and weather conditions. In high-density microalgae cultures of photobioreactors outdoors, on top of natural variations, microalgae are subjected to further complexity in light exposure. Because of the high-density cells experience self-shading effects that heavily limit light availability in most of the mass culture volume. This limitation strongly affects biomass productivity of industrial microalgae cultivation plants with important implications on economic feasibility. Understanding how photosynthesis responds to cell density is informative to assess functionality in the inhomogeneous light environment of industrial photobioreactors. In this work we exploited a high-sensitivity Clark electrode to measure microalgae photosynthesis and compare cultures with different densities, using Nannochloropsis as model organism. We observed that cell density has a substantial impact on photosynthetic activity, and demonstrated the reduction of the cell's light-absorption capacity by genetic modification is a valuable strategy to increase photosynthetic functionality on a chlorophyll-basis of dense microalgae cultures.

Lipids productivity of cyanobacterium Anabaena vaginicola in an internally illuminated photobioreactor using LED bar lights.

Concerns over environmental issues exists and desire to decrease of their extent, have directed efforts toward green energy production. Growth behavior of Anabaena vaginicola was determined in a photobioreator which illuminated internally (IIPBR) using LED bar light. Excessive heat generated in the IIPBR was taken care of by applying a novel air-cooled system. Further note in experimentation was to find favorable cultivation conditions in the IIPBR for A. vaginicola growth and its lipids production capacity. The following results are expressed: 80 µmol photons m-2 s-1 as light intensity, 0.5 g/l as NaNO3, and 120 ml/min as CO2 amount being expressed in terms of aeration rate. The findings were interpreted in terms of a two-component system where the genes encoded to the relevant proteins are present in cyanobacteria and their expressiveness depends on environmental stress. By determining growth rate constant as 0.11 d-1, the productivity in terms of biomass formation was calculated as 202.6 mg L-1 d-1. While rate of lipids production by the test cyanobacterium is 15.65 mg L-1 d-1. Based on total energy used for IIPBR performance, biomass productivity per unit power input equals to 0.74 g W-1 d-1 and this is in favorable position compared with other photobioreactors.

A comprehensive review on effective parameters on microalgae productivity and carbon capture rate.

Rising carbon emissions caused by population growth and industrialization is a significant environmental challenge in various countries. To combat this issue, Renewable Energy (RE) and Carbon Capture and Storage (CCS) technologies should be commercialized to reduce Greenhouse Gas (GHG) emissions and generate carbon-free energy. One such technology is the use of microalgae, which can directly capture CO2 from the air through photosynthesis and potentially produce biofuels due to their high energy content. However, the carbon capture rate of microalgae varies globally due to numerous parameters and variables affecting microalgae productivity. Additionally, microalgae productivity and carbon capture formulas yield different results worldwide, especially in outdoor industrial-scale cultivation. This research aims to comprehensively review the effective variables and parameters in carbon capture by microalgae based on microalgae productivity and carbon capture formulas. The research also ranked countries based on CO2 production in four different categories to determine whether the biggest carbon producer countries could exhibit suitable weather conditions for microalgae cultivation. Findings reveal optimal ranges of critical variables in the microalgae growth formula, including temperature, solar radiation intensity, Photon Flux Density (PFD), and sunlight duration. The study also analyzes microalgae cultivation, carbon capture, and oxygen production formula in different systems such as Open Ponds (OP), Tubular Photobioreactors (TPBR), and Flat Plate Photobioreactors (FPPBR), while discussing other influential parameters. In conclusion, emphasizing the adjustment and utilization of optimal values of effective parameters in microalgae cultivation not only holds promise for future carbon capture by microalgae but also pushes human beings toward sustainable development goals.

Removal of contaminants of emerging concern from pig manure in different operation stages of a thin-layer cascade photobioreactor. Relationship with concentrations in microalgae and manure.

The performance of a pilot-scale thin-layer cascade photobioreactor, operated in semicontinuous mode, for the removal of veterinary drug residues and other contaminants of emerging concern (CECs) from pig manure has been assessed in six operation stages. Chlorella sp. (70-90%), Scenedesmus sp. (10-25%) and Diatomea (<5%) comprise the microalgae species present during the stages. The global performance to remove the total CEC content in the photobioreactor effluent varied from 62 to 86% on each stage, while an CEC mean amount close to 8% was accumulated in the photobioreactor biomass. A relation with weather conditions was not observed. Elimination ratio was not related to the concentration in the influent which reached up to 8000 ng L-1 for some CECs. As expected, the concentrations of veterinary drugs were higher than those of non-veterinary CECs. The concentrations accumulated in the grown biomass were relative low, lower than 10 ng per fresh g excepting for a few cases. However, statistical data suggested that the linkage of CECs to microalgae biomass boosted their removal from the influent. Furthermore, it was observed that the manure liquid phase contained higher amounts of CECs than the solid phase.

Dialysis bag-microalgae photobioreactor: Novel strategy for enhanced bioresource production and wastewater purification.

Cultivating microalgae in wastewater offers various advantages, but it still faces limitations such as bacteria and other impurities in wastewater affecting the growth and purity of microalgae, difficulty in microalgae harvesting, and extracellular products of microalgae affecting effluent quality. In this study, a novel dialysis bag-microalgae photobioreactor (Db-PBR) was developed to achieve wastewater purification and purer bioresource recovery by culturing microalgae in a dialysis bag. The dialysis bag in the Db-PBR effectively captured the microalgae cells and promoted their lipid accumulation, leading to higher biomass (1.53 times of the control) and lipid production (2.50 times of the control). During the stable operation stage of Db-PBR, the average soluble microbial products (SMP) content outside the dialysis bag was 25.83 mg L-1, which was significantly lower than that inside the dialysis bag (185.63 mg L-1), indicating that the dialysis bag effectively intercepted the SMP secreted by microalgae. As a result, the concentration of dissolved organic carbon (DOC) in Db-PBR effluent was significantly lower than that of traditional photobioreactor. Furthermore, benefiting from the dialysis bag in the reactor effectively intercepted the microorganisms in wastewater, significantly improving the purity of the cultured microalgae biomass, which is beneficial for the development of high-value microalgae products.

Methods for the separation of hydraulic retention time and solids retention time in the application of photosynthetic microorganisms in photobioreactors: a review.

Photosynthetic microorganisms have a wide range of biotechnical applications, through the application of their versatile metabolisms. However, their use in industry has been extremely limited to date, partially because of the additional complexities associated with their cultivation in comparison to other organisms. Strategies and developments in photobioreactors (PBRs) designed for their culture and applications are needed to drive the field forward. One particular area which bears examination is the use of strategies to separate solid- and hydraulic-residence times (SRT and HRT), to facilitate flow-through systems and continuous processing. The aim of this review is to discuss the various types of PBRs and methods which are currently demonstrated in the literature and industry, with a focus on the separation of HRT and SRT. The use of an efficient method of biomass retention in a PBR may be advantageous as it unlocks the option for continuous operation, which may improve efficiency, and improve economic feasibility of large-scale implementation of photosynthetic biocatalysts, especially where biomass is not the primary product. Due to the underexplored nature of the separation of HRT and SRT in reactors using photosynthetic microorganisms, limited literature is available regarding their performance, efficiencies, and potential issues. This review first introduces an overview into photosynthetic microorganisms cultivated and commonly exploited for use in biotechnological applications, with reference to bioreactor considerations specific to each organism. Following this, the existing technologies used for the separation of HRT and SRT in PBRs are explored. The respective advantages and disadvantages are discussed for each PBR design, which may inform an interested bioprocess engineer.

Biomass productivity and characterization of Tetradesmus obliquus grown in a hybrid photobioreactor.

In this study, the effects of CO2 addition on the growth performance and biochemical composition of the green microalga Tetradesmus obliquus cultured in a hybrid algal production system (HAPS) were investigated. The HAPS combines the characteristics of tubular photobioreactors (towards a better carbon dioxide dissolution coefficient) with thin-layer cascade system (with a higher surface-to-volume ratio). Experimental batches were conducted with and without CO2 addition, and evaluated in terms of productivity and biomass characteristics (elemental composition, protein and lipid contents, pigments and fatty acids profiles). CO2 enrichment positively influenced productivity, and proteins, lipids, pigments and unsaturated fatty acids contents in biomass. The HAPS herein presented contributes to the optimization of microalgae cultures in open systems, since it allows, with a simple adaptation-a transit of the cultivation through a tubular portion where injection and dissolution of CO2 is efficient-to obtain in TLC systems, greater productivity and better-quality biomass.

A robust multinutrient kinetic model for enhanced lutein and biomass yields in mixotrophic microalgae cultivation: A step towards successful large-scale productions.

Mixotrophic cultivation holds great promise to significantly enhance the productivities of biomass and valuable metabolites from microalgae. In this study, a new kinetic model is developed, explicitly describing the effect of the most influential environmental factors on both biomass growth and the production of the high-value product lutein. This extensive study of multinutrient kinetics for Tetradesmus obliquus in a mixotrophic regime covers various nutritional conditions. Crucial nutrients governing the model include nitrate, phosphate, and glucose. Using seven state variables and 13 unknown parameters, the model's accuracy was ensured through a well-designed two-factor, four-level experimental setup, providing ample data for reliable calibration and validation. Results accurately predict dynamic concentration profiles for all validation experiments, revealing broad applicability. Optimizing nitrogen availability led to significant increases in biomass (up to fourfold) and lutein production (up to 12-fold), with observed maximum biomass concentration of 6.80 g L-1 and lutein reaching 25.58 mg L-1. Noticeably, the model exhibits a maximum specific growth rate of 4.03 day-1, surpassing reported values for photoautotrophic and heterotrophic conditions, suggesting synergistic effects. Valuable guidance is provided for applying the method to various microalgal species and results are large-scale production-ready. Future work will exploit these results to develop real-time photobioreactor operation strategies.

Perspectives on cultivation and harvesting technologies of microalgae, towards environmental sustainability and life cycle analysis.

The development of algae is seen as a potential and ecologically sound approach to address the increasing demands in multiple sectors. However, successful implementation of processes is highly dependent on effective growing and harvesting methods. The present study provides a complete examination of contemporary techniques employed in the production and harvesting of algae, with a particular emphasis on their sustainability. The review begins by examining several culture strategies, encompassing open ponds, closed photobioreactors, and raceway ponds. The analysis of each method is conducted in a systematic manner, with a particular focus on highlighting their advantages, limitations, and potential for expansion. This approach ensures that the conversation is in line with the objectives of sustainability. Moreover, this study explores essential elements of algae harvesting, including the processes of cell separation, dewatering, and biomass extraction. Traditional methods such as centrifugation, filtration, and sedimentation are examined in conjunction with novel, environmentally concerned strategies including flocculation, electro-coagulation, and membrane filtration. It evaluates the impacts on the environment that are caused by the cultivation process, including the usage of water and land, the use of energy, the production of carbon dioxide, and the runoff of nutrients. Furthermore, this study presents a thorough examination of the current body of research pertaining to Life Cycle Analysis (LCA) studies, presenting a perspective that emphasizes sustainability in the context of algae harvesting systems. In conclusion, the analysis ends up with an examination ahead at potential areas for future study in the cultivation and harvesting of algae. This review is an essential guide for scientists, policymakers, and industry experts associated with the advancement and implementation of algae-based technologies.

Design parameters comparison of bubble column, airlift and stirred tank photobioreactors for microalgae production.

Microalgae are the most propitious feedstock for biofuel production due to their lipid and fatty acid content. Microalgae cultivation shares many features with bioreactors, such as thermal and pH regulation, feeding procedures, and mixing to enhance heat and mass transfers. Aeration and stirring speeds are important parameters to reduce the costs of producing microalgae. In this study, three different photobioreactor types (stirred tank, airlift, bubble column) were characterized and compared for microalgae production. Hydrodynamics, mass transfer, and power consumption were determined for various aeration rates (0.9, 1.2, 1.5 L/min), and stirring speeds (100, 200 rpm), and Chlorella sorokiniana growth performance was compared under the conditions that provided the highest volumetric mass transfer and the lowest mixing time. Photo-bioreactor homogenization was good as indicated by low mixing times (< 10 s). Bubble column had the highest volumetric mass transfer due to its sparger design. Gas holdup and volumetric mass transfer coefficient were found to increase with the air flow rate and stirring speed. For stirred tank, bubble column, and airlift photobioreactors, maximum specific growth rates of C. sorokiniana were 0.053, 0.061, 0.057 h-1, and biomass productivities were 0.064, 0.097, 0.072 gdw/L.day, respectively. Under the conditions tested, growth was limited by the volumetric mass transfer in the airlift and stirred tank and bubble column was the best option for producing microalgae. These findings pave way for more extensive use of these systems in producing microalgae and provide a basis to compare photobioreactors of different designs.

Biological performance and membrane fouling of a microalgal-bacterial membrane photobioreactor for wastewater treatment without external aeration and carbonation.

Biological nutrient removal processes involving the use of activated sludge (AS) to treat municipal wastewater normally result in high aeration energy consumption and significant greenhouse gas (GHG) emissions. Therefore, developing cost-efficient and environmentally friendly processes for wastewater treatment is vital. In this work, a novel non-aerated microalgal-bacterial membrane photobioreactor (MB-MPBR) was proposed, and its feasibility for organic contaminant and nutrient removals was evaluated, for the first time. The effects of inoculation ratio (microalgae to bacteria (M/B)) on the biological performance and membrane fouling were systematically investigated. The results showed that 95.9% of the chemical oxygen demand (COD), 74.5% of total nitrogen (TN), 98.5% of NH4+-N and 42.0% of total phosphorus (TP) were removed at an inoculation M/B ratio of 3:2 at steady state, representing a significant improvement compared to the M/B inoculation ratio of 1:3. Additionally, the higher inoculation M/B ratio (3:2) significantly promoted the biomass production owing to the favorable mutual exchange of oxygen and carbon dioxide between microalgae and bacteria. Cake layer formation was the primary fouling mechanism owing to the absence of aeration scouring on the membrane surface. The membrane fouling rate was slightly higher at the higher inoculation ratio (M/B = 3:2) owing to the increased biomass and extracellular polymeric substances (EPS) productions, despite the larger particle size. These results demonstrated that the non-aerated MB-MPBR could achieve superior biological performance, of which the inoculation M/B ratio was of critical importance for the initiation and maintenance of microalgal-bacterial symbiotic system, yet possibly caused severer membrane fouling in the absence of external aeration and carbonation. This study provides a new perspective for further optimizing and applying non-aerated MB-MPBR to enhance municipal wastewater treatment.

Systematic assessment of wastewater resource circularity and sustainable value creation.

The circular use of wastewater has attracted significant attention in recent years. However, there is a lack of universal definitions and measurement tools that are required to achieve the circular economy's full potential. Therefore, a methodology was developed using three indicator typologies, namely resource flow, circular action, and sustainability indicators, to facilitate a robust and holistic circularity assessment. The method uses value propositions to integrate the assessment of intrinsic circularity performance with consequential circularity impacts, by quantifying sustainable value creation (using techniques such as life cycle assessment or cost-benefit analysis). Assessment method capabilities were exhibited by applying the defined steps to a wastewater treatment plant, comparing conventional and novel photobioreactor technologies. The resource flow indicator taxonomy results highlight improved outflow circularity, renewable energy usage, and economic efficiency of the novel system. Action indicators revealed that the photobioreactor technology was successful at achieving its defined circular goals. Lastly, sustainability indicators quantified a reduction of carbon footprint by two thirds and eutrophication by 41%, a M€ 0.5 per year increase of economic value, and that disability adjusted life year impacts are 58% lower. This supports that improving wastewater system circularity using photobioreactor technology results in environmental, economic, and social value for stakeholders.

A vertical-flow constructed wetland-microalgal membrane photobioreactor integrated system for treating high-pollution-load marine aquaculture wastewater: A lab-scale study.

Individual biological water treatment techniques often prove ineffective in removing accumulated high concentrations of nitrogen and phosphorus in the late stages of biofloc aquaculture. To address this issue, we integrated a previously developed autotrophic denitrification and nitrification integrated constructed wetland (ADNI-CW) with a microalgal membrane photobioreactor (MPBR). Under high nitrogen and phosphorus pollution loads in the influent, the standalone ADNI-CW system achieved removal rates of only 24.17 % ± 2.82 % for total nitrogen (TN) and 25.30 % ± 2.59 % for total phosphorus (TP). The optimal conditions for TN and TP degradation and microalgal biomass production in the Chlorella MPBR, determined using response surface methodology, were an inoculum OD680 of 0.394, light intensity of 161.583 µmol/m2/s, and photoperiod of 16.302 h light:7.698 h dark. Under the optimal operating conditions, the integrated ADNI-CW-MPBR system achieved remarkable TN and TP removal rates of 92.63 % ± 2.8 % and 77.46 % ± 8.41 %, respectively, and a substantial microalgal biomass yield of 54.58 ± 6.8 mg/L/day. This accomplishment signifies the successful achievement of efficient nitrogen and phosphorus removal from high-pollution-load marine aquaculture wastewater along with the acquisition of valuable microalgal biomass. A preliminary investigation of the microbial community composition and algal-bacterial interactions in different operational stages of the MPBR system revealed that unclassified_d__Bacteria, Chlorophyta, and Planctomycetes were predominant phyla. The collaborative relationships between bacteria and Chlorella surpassed competition, ensuring highly efficient nitrogen and phosphorus removal in the MPBR system. This study laid the foundation for the green and sustainable development of the aquaculture industry.

Artificial neural networks prediction and optimization based on four light regions for light utilization from Synechocystis sp. PCC 6803.

Light is crucial in microalgae growth. However, dividing the microalgae growth region into light and dark regions has limitations. In this study, the light response of Synechocystis sp. PCC 6803 was investigated to define four light regions (FLRs): light compensation region, light limitation region, light saturation region, and photoinhibition region. The proportions of cells' residence time in the FLRs and the number of times cells (NTC) passed through the FLRs in photobioreactors were calculated by using MATLAB. Based on the FLRs and NTC passed through the FLRs, a growth model was established by using artificial neural network (ANN).The ANN model had a validation R2 value of 0.97, which was 76.36% higher than the model based on light-dark regions. The high accuracy of the ANN model was further verified through dynamic adjustment of light intensity experiments.This study confirmed the importance of the FLRs for studying microalgae growth dynamics.

Influence of super-optimal light intensity on the acetic acid uptake and microalgal growth in mixotrophic culture of Chlorella sorokiniana in bubble-column photobioreactors.

This study seeks to determine the influence of super-optimal light intensity on acetic acid uptake and its associated impact on the cellular composition of Chlorella sorokiniana in a semi-batch mixotrophic cultivation setup. Unicellular green microalga Chlorella sorokiniana is grown in a 1L bubble-column photobioreactor at light intensities from 6000 to 14,000 lx (≈81 to 189 µmol.photons.m-2.s-1). We find that microalgal acetic acid utilization reduces as illumination increases from an optimal 10,000 lx (≈135 µmol.photons.m-2.s-1) to a super-optimal zone (>10000 lx). This lowers microalgal growth (2.75 g/L) and acetic acid intake, which peak at 6 mL/L (10000 lx) and drop to 2 and 1 mL/L at 12,000 and 14,000 lx, respectively. Concurrently, the maximum lipid yield decreases from 0.66 g/L (10000 lx) to 0.54 g/L (12000 lx) and 0.42 g/L (14000 lx). Hence, super-optimal illumination not only disturbs phototrophy but also affects the heterotrophic component, creating an imbalance between the two.