Processing Of Microalgae Research Articles

A learning-based model predictive strategy for pH control in raceway photobioreactors with freshwater and wastewater cultivation media

This article presents a study on the pH control of raceway photobioreactors (PBRs) using a learning-based model predictive control (LBMPC) approach. The primary objective is to enhance the control performance and improve microalgae biomass production. The research builds upon existing control solutions for PBRs found in the literature by integrating the robust and adaptive capabilities of the LBMPC. Specifically, the control algorithm is modified to include a pre-established Linear Quadratic Tracking with a Feedforward controller, facilitating the formulation of the conventional LBMPC. To validate the proposed controller, implementation is performed in an existing facility at the IFAPA center, located near the University of Almería in Southern Spain. The experiment involves two parallel PBRs operating under the same meteorological conditions with different microalgae strains and media (freshwater and wastewater). The LBMPC demonstrates satisfactory results and is compared with the conventional nominal MPC strategy through an analogous experiment. The LBMPC outperforms the conventional approach, achieving up to four times superior performance in terms of the average error index. The results highlight the importance of employing robust adaptive control strategies for highly nonlinear and multi-disturbed systems like the variant biological-chemical microalgae process in PBRs since the complexity associated with adapting the system’s model can negatively impact the performance of conventional model-based controllers.

Spirulina and Its Potential in Bioproduct Production: a Review

The use of the microalgal biomass in biorefineries can produce different products, such as biofuel, food, feed, and bioactive compounds. In addition, the microalgae used in waste treatment can have its biomass exploited, such as Spirulina sp., which shows satisfactory results in the studies performed. Thus, the present study aimed to describe the production of Spirulina bioproducts in biorefineries, demonstrating its benefits and its potential for sustainable development. The study utilized an integrative literature review methodology, and the research question was "What bioproducts can be developed from a Spirulina biorefinery and how can they contribute to sustainability?". The articles were initially screened based on their title and abstract, and only those that fit the research question were selected for full reading. The reviewed studies suggest that the processing of microalgae within biorefineries has significant potential for synergy, sustainable processes can be developed that maximize the use of microalgae biomass and minimize waste and emissions. Spirulina can be used to treat wastewater from food processing plants, where microalgae could absorb nutrients and organic matter while producing biomass that could be harvested and converted into other bioproducts. However, challenges such as high operating costs, variability in biomass and effluent composition, and the need for scalable technologies must be addressed to fully realize the benefits of microalgae in biorefineries. Further research and investment in this area are necessary to develop cost-effective, scalable, and sustainable microalgae biorefineries, involving interdisciplinary collaborations between different fields and partnerships between academia, industry, and government.

Evaluation of efficiency of disruption methods for Coelastrella sp. in order to obtain high yields of biochemical compounds release

Downstream processes in microalgae, such as the extraction of high value-added compounds, are often hampered by the intrinsic rigidity of the cell wall. The toughness of this structure makes the intracellular compounds less available for extraction, which means that cell disruption methods are necessary to apply. Coelastrella sp. is a terrestrial microalga that reveals to be a promising source of bioactive compounds; however, due to its extremely resistant wall, few extraction and determination studies of these compounds have been performed. In order to maximize the extraction efficiency and be as energy-efficient as possible, five different cell disruption methods have been optimized: Freeze-Thaw cycles – ten freezing cycles at −80 °C and thawing at 40 °C; Bead Milling – 32 % (in volume) of beads (0.5 mm) and treatment time of 6 min; High-speed homogenization - 25,000 rpm for 80 min; Microwave – 800 W for 12 min; and Sonication – 40 kHz for 60 min.Sonication and bead milling proved to be the most efficient processes in cell disruption and intracellular organic matter release, with a value of 9.6 and 5.4, respectively. In addition to these two methods, which yielded rupture efficiencies above 90 % after the application of the treatment, High-speed homogenization also showed a disruption efficiency of around 90 %. On the other hand, microwave and freeze-thaw cycles had a low impact on Coelastrella sp. cells, allowing the surviving of about 39 % and 66 % of the initial sample, respectively. Sonication showed the highest efficiency in the release of proteins, carbohydrates and lipids, always followed by bead milling as the most efficient. Freeze-thaw cycles have shown to be the most efficient in releasing phenolic compounds, whereas microwave was the most inefficient in releasing biochemical compounds overall.Considering the results obtained and the energy consumption in each treatment, bead milling can be considered the most efficient method.

Efficient anaerobic digestion of hydrothermal carbonization wastewater via an innovative multistage anaerobic hythane reactor (MAHR): Organic conversion and microbial evolution

Seeking continuous treatment of downstream wastewater is a desperate requirement for the scale-up of hydrothermal technology. In this study, a novel multistage anaerobic hythane reactor (MAHR), which was constructed with an internal downflow biofilter bed and an external up-flow sludge bed, was used to dispose of hydrothermal carbonation wastewater (HTCWW), a by-product of the hydrochar preparation process of microalgae. To verify the performance of MAHR for the actual complex wastewater treatment, a conventional up-flow anaerobic sludge bed reactor (UASB) was used as a comparison. The two reactors were both operated independently in parallel with a hydraulic retention time (HRT) of 12 h and an organic load rate (OLR) of 20 g SCOD/L/d. Both MAHR and UASB achieved 84% COD removal rate and 7.0 ± 0.6 and 5.5 ± 0.3 L/L/d of methane production rate, respectively, when the proportion of HTCWW was increased to 100% of the original wastewater. Specifically, the hythane-producing area (MH) of MAHR was gradually transformed into methane producing area in the process of feeding HTCWW. High-performance liquid chromatography (HPLC) analysis revealed that more small molecule compounds including organic acids and inhibitors were degraded in MAHR. Fourier transform ion cyclone resonance mass spectrometry (FT-ICR MS) analysis demonstrated that more soluble proteins and lipids were degraded to some extent, while the lignin and condensed aromatic compounds increased especially in UASB. A dramatic change was observed in the dominating microbial communities in MAHR and UASB from the Streptococcaceae associated with carbohydrates degradation to the Renkenellaceae involved in both proteins and carbohydrates degradation. At the archaeal level, hydrogenotrophic methanogens replaced acetoclastic methanogens. Redundancy analysis (RDA) further verified the relationship between dominant functional communities and the anaerobic digestion performance of the reactors. The above results indicate that MAHR is a promising configuration for the anaerobic valorization of hydrothermal wastewater.

Expanded utilisation of microalgae in global aquafeeds

AbstractUtilising novel ingredients in aquafeeds is necessary for the continued expansion and intensification of aquaculture production. Microalgae are utilised widely in aquaculture for a variety of purposes; as live feed for fish and shellfish larvae and juveniles, for the production of algae‐based meals and oils to replace marine derived raw materials in aquafeeds, and for the production of astaxanthin, the carotenoid that gives salmon flesh its characteristic reddish colour. Notably, long‐chain polyunsaturated fatty acids, amino acids, proteins, fibres, antioxidant pigments, vitamins and minerals are among the compounds in microalgae with great biological value. A growing collection of experimental data has demonstrated that these substances are crucial for increasing larval survival and enhancing the growth and well‐being of fish and shellfish. In this review, the processing of microalgae utilised as aquafeed ingredient, the health promoting compounds in microalgae and their role in growth, immunity and disease resistance of fish and shellfish are described and discussed. Simultaneously, major hurdles in the commercial use of microalgae in aquafeed, and future research and development perspectives are all critically discussed.

Feasibility of a self‐sustaining microbial fuel cell incorporating natural processes of bacteria and microalgae towards a circular bioeconomy

AbstractA microbial fuel cell (MFC) consisting of a bacterial anode chamber and a microalgal cathode chamber was operated under various conditions to assess its technical feasibility. Maximum achievable power density reached up to 7.13 mW m–2. The traditional MFC process of conversion of carbon sources to bioelectricity in the anodic chamber was compared with a system circulating anodic effluent to the cathode chamber. The bacteria and microalgae simultaneously carried out the carbon recycling and recovery of energy and resources synergizing the performance of MFC. Results indicated a comparable chemical oxygen demand removal efficiencies at 50% of the retention time compared to the traditional system. The dissolved oxygen concentration varied between 11.95 and 7.44 mg L–1 with Chlorella vulgaris under alternative light and dark cycles. Despite the variations in electricity output, the system showed its technical feasibility to harness energy for photosynthesis under natural sunlight conditions.

LED Illumination Modules Enable Automated Photoautotrophic Cultivation of Microalgae in Parallel Milliliter-Scale Stirred-Tank Bioreactors

Scalable lab-scale photobioreactors are needed for the exploration of new and improved photoautotrophic bioprocesses. Microbioreactor systems in which parallel bioreactors operate automatically are frequently employed to increase the speed of strain selection as well as the bioprocess-based exploration of heterotrophic fermentation processes. To enable the photoautotrophic operation of a commercially available parallel microbioreactor system with 48 stirred-tank bioreactors, LED illumination modules were designed to allow for individual light supply (400–700 nm) for each of the parallel bioreactors automated by a liquid handling station that performs both individual pH control and OD750 detection. The illumination modules enable dynamic variation of the incident light intensities of up to 1800 µmol m−2 s−1. Automated liquid level detection and volume control of each individual mL-scale gassed photobioreactor has to be established to compensate for evaporation because of the long process times of several days up to weeks. Photoautotrophic batch processes with Microchloropsis salina that employ either varying constant incident light intensities or day and night dynamics resulted in a standard deviation of OD750 of up to a maximum of 10%, with the exception of high-photoinhibiting incident light intensities. The established photoautotrophic microbioreactor system enables the automated investigation of microalgae processes in up to 48 parallel stirred photobioreactors and is thus a new tool that enables efficient characterization and development of photoautotrophic processes with microalgae.

Microstructure Engineered Photon‐Managing Films for Solar Energy to Biomass Conversion

AbstractConversion of solar energy into chemical energy through natural photosynthesis plays a crucial role in sustainable energy transformation, bioresource production, and CO2 biofixation. Nevertheless, the overall solar energy to chemical energy (biomass) conversion efficiency in the photosynthetic organisms is still unsatisfactory because of their inefficient utilization of solar light. Here, a photonic method to improve photosynthesis of a unicellular green microalga, Chlamydomonas reinhardtii, a photosynthetic organism model is reported. For this purpose, an easy‐to‐fabricate microphotonic film is developed to improve the spectral quality of solar light reaching the microalgae through photon management (i.e., simultaneous solar spectral conversion and directional fluorescent emission). This study demonstrates that the short‐term oxygen evolution rate and the long‐duration biomass production of microalgae in 200‐mL laboratory photobioreactors are enhanced by a factor of 38% and 54%, respectively. In 5000‐mL scaled‐up bubble column photobioreactors placed outdoor under natural sunlight and weather conditions, the biomass yield is improved by more than 20% when compared to the control experiments conducted in parallel in an optically clear bubble column photobioreactor. Based on such experimental observations, the work here demonstrates the potential of photon management for promoting the solar energy‐to‐biomass conversion process of microalgae and other photosynthetic organisms.

The N:Chl-a ratio defines the optimal physiological state in marine microalgae

Several factors may influence the growth of microalgae and their biochemical composition. Thus, bioassays can contribute to understanding how the environment influences the chemical element:chlorophyll-a ratio and the metabolic processes in different microalgae. The objective of this study, under laboratory conditions, was to study the variation in the Carbon-to-Chlorophyll-a (C:Chl-a), Nitrogen-to-Chlorophyll-a (N:Chl-a), and Hydrogen-to-Chlorophyll-a (H:Chl-a) ratios as indicators of the physiological state of species representative of different functional groups of phytoplankton: Isochrysis galbana, Chaetoceros calcitrans, and Dunaliella tertiolecta. The results suggest that changes in the content of intracellular pigments can be directly attributed to maximizing phytoplankton growth through the metabolic requirements, where Nitrogen and Carbon uptake and assimilation are critical drivers related to their physiological needs rather than their photosynthesis processes per se. Our observations documented the behavior of phytoplanktonic microalgae, where I. galbana showed the lowest Chl-a values associated with metabolic processes to produce complex molecules for storage and as reserve compounds. In C. calcitrans, metabolic processes are mainly addressed to generate complex compounds of Carbon and Nitrogen inside the cell rather than for population increase. Finally, D. tertiolecta showed that these elements are used gradually but progressively, generating more photosynthetic units during the exponential growth phase. This work provides new evidence to understand metabolic mechanisms between different groups of phytoplankton, essential knowledge to produce macromolecules and bioactive metabolites with different applications.

Carotenoid Profile of Freshwater Microalgae Mychonastes racemosus AUP1 and its Antioxidant properties

Microalgae contain some active compounds that can be used for various purposes, such as carotenoids and high-value compounds with antioxidant capacity to be used as ingredients for food and pharmaceuticals This study aims to isolate microalgae from freshwater to produce carotenoid pigments. A green microalga was isolated from a local freshwater pond. Morphological observation and molecular analysis were performed to identify the microalgae. The molecular phylogenetic analysis was conducted based on the sequences of 18S rRNA genes. The carotenoid pigments were then extracted from the microalgae using water: methanol: dichloromethane (1:2:1,v/v/v). Further carotenoid pigments were then characterized using ultraviolet–visible (UV–Vis) spectrophotometry, FTIR, and HPLC. The antioxidant activity of the microalgae carotenoid extracts was determined with the 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) radical scavenging assay. The results showed that the microalgae belong to the species Mychonastes racemosus AUP1. Carotenoid extracts was obtained from microalgae were about to 86 mg/g dry weight extract was obtained from extraction process of microalgae. Based on FTIR, and HPLC analysis, the microalgae carotenoid extracts contained β-carotene (C40H56) and lutein (C40H56O4). The IC50 value of microalgae carotenoid extract was 78.61 µg/mL. This study suggests that microalgae Mychonastes racemosus AUP1 are potential sources for obtaining carotenoid with strong antioxidant activity. In the future, the microalgae Mychonastes racemosus AUP1 has the potential for prospection of functional foods.

Holistic exploitation of pulsed electric field (PEF)-treated and lipid extracted microalgae Auxenochlorella protothecoides, utilizing anaerobic digestion (AD)

This study proposes a cascade processing of the lipid-rich microalgae Auxenochlorella protothecoides. Freshly harvested biomass is pre-concentrated to 100 g/kgsusp and then pretreated using pulsed electric fields (PEF). PEF-treatment, which affects permeability of cells membrane, induces a spontaneous release of microalgal ingredients into the surrounding medium, mostly carbohydrates and micronutrients, which can be recovered. After separation of this aqueous fraction, lipid extraction is performed on the remaining wet pellet using an ethanol-hexane blend. After recovery of those different valuables, it was considered, to convert the rest biomass (cell envelope and most of the other remaining hard- or non-extractable components), to storable energy. Anaerobic digestion (AD) of the remains to biogas was considered to be a promising solution. AD-processes have the charm that unprocessed wet microalgal biomass, as well as wet organic biomass residues from previous extraction steps can be utilized directly without further purification or drying steps. The obtained biogas can then be upgraded to methane for an energetic use.PEF-treated algal biomass showed a 10 % increased methane outcome (467 mLnorm/gVS) compared to the untreated sample. PEF-treated microalgae, subjected to extraction of the aqueous fraction, demonstrated a 23 % increase in methane yield (558 mLnorm/gVS), compared to control. Finally, the biomass, PEF-treated and subjected to extraction of water fraction and lipids, still achieved 41 % of methane potential (205 mLnorm/gVS) during the AD process, compared to the untreated control.Our study demonstrates the feasibility of cascade processing using PEF-treatment. Moreover, all the study was developed keeping in mind industrial requirements. In particular, our downstream approach did not require any drying, the pretreatment required low amount of energy, i.e. 1.5 MJ/kgCDW and the majority of the biomass was valorized. Since all techniques used, especially PEF-pretreatment, can be up-scaled, we believe this approach has great potential for implementation in industry.

A Study Exploring the Effects of Cell Disruption Techniques on Lipid Recovery in Co-cultivated Microalgae and Oleaginous Yeast

Co-cultivation and effective downstream processing of microalgae and oleaginous yeast are potential strategies to enhance lipid yield. The findings of this work suggest that each cultivable partner should be screened and optimized for the best mutualistic co-cultures. In this case, T. pullulans was found to be the most effective yeast culture with microalgae S. obliquus, C. sorokiniana, and C. protothecoides along with additional cell disruption techniques. Co-cultures of C.protothecoides and T.pullulans had the highest relative lipid yield (RLY) of 68.71%, 59.32%, 55.33%, 53.19%, and 47.3% with sonication, microwave, osmotic shock, freeze-drying, and autoclave, respectively. Sonication was concluded as the best disruption technique with five out of nine co-cultures showing significant lipid enhancement. Even though T. pullulans was the best yeast partner with disruption techniques, co-culture of Y. lipolytica and S.obliquus (RLY 37.11%) produced lipids which was significantly higher than that of their respective monocultures (S. obliquus RLY 23.96%, Y. lipolytica RLY 4.96%) without any disruption process. R. glutinis and Y. lipolytica produced significantly enhanced lipid yield with C.sorokiniana and S. obliquus with sonication (RLY 51.44%) and osmotic shock (RLY 57.70%), respectively. FAME analysis reported that the co-cultures produced higher percentage of total FAME nearly 100% in the case of C. sorokiniana and R. glutinis with high content of saturated fatty acids (SFAs). The presence of biofuel precursors like palmitic acid, linoleic acid, oleic acid, and heptadecanoic acid, confirms their suitability for biofuel production.Graphical Abstract

Evaluation of The Biochemical Contents in Guillard f/2 and Walne Growth Medium to Fulfill the Animal-Free Aspects of Microalgal Bioprocessing

Marine microalgae with their diverse biomolecule contents could be used as potential sources of food, cosmetics, and pharmaceutical ingredients. In accordance with regulations in some countries and to competitively engage huge numbers of consumers, microalgae-based products should be properly manufactured using non-animal-derived materials. As a cultivable microorganism using a scalable bioreactor technique, consideration of the origin of the material used in the upstream process of marine microalgae was inevitable. Currently, the material origin of chemical contents within common artificial microalgal seawater medium had not been evaluated. This article evaluated Guillard f/2 and Walne medium as common artificial microalgal nutrients used in marine microalgal bioprocess-related activities. The risk assessment results showed that the largest portion of Guillard f/2 and Walne media were inorganic salts considered as low, while the remaining biochemical contents of vitamins were categorized as high risk due to their relatively complex chemical synthesis and enzymatic stages during the manufacturing process. As a suggestion, several plant-based bioproducts were proposed as alternative sources to substitute related biochemical actions to fulfill non-animal-origin aspects in the initial stages of the bioprocessing of marine microalgal-based products.

Waste carbon conversion and utilization in chemical wastewater treatment process: Experimental approaches from lab-to pilot-scale

Chemical wastewater often contains large amounts of waste organic carbon. The current chemical wastewater treatment plants are an open carbon emission system. Inspired by the topic of CO2 conversion and utilization, this study provided a redesigned flowchart of chemical wastewater treatment process via closed-loop carbon conversion and utilization system for the resource utilization of waste carbon from wastewater. Purified terephthalic acid (PTA) wastewater, a common chemical wastewater, was selected to test the feasibility of the proposed strategy. An integrated closed-loop system involving activated sludge-microalgae-pyrolysis process was employed. Initially, a laboratory-scale wastewater treatment system combining activated sludge with microalgae process was applied for the carbon conversion and utilization in PTA wastewater. The COD removal efficiency was obtained at 93.02%, and over 94% of CO2 was captured. Microbial DNA analysis of the activated sludge indicated that the functional microorganisms mainly included Proteobacteria, Bacteroidetes, and Chloroflexi. Metabolic analysis of the microalgae showed that the abundances of differential metabolites associated with carbon metabolism significantly increased after treatment. Furthermore, a pilot-scale integrated system was applied to test this strategy and in which obtained a good performance in COD removal and CO2 capture. The produced excess biomass during chemical wastewater treatment, which was usually viewed as hazardous solid waste, was converted to biochar and carbonaceous combustible gas via pyrolysis. The produced biochar could be used as photocatalysts to remove antibiotic. The findings provided a new design to simultaneously achieve water pollution control, carbon conversion & utilization, and resource & energy recovery in chemical wastewater treatment process.

Growth and Physiological Responses of Chrysotila roscoffensis (Coccolithales) to Different Phosphorus Resources

The growth and physiological process of microalgae interact with environmental nutrients. In the present study, we compared the growth and physiological characteristics of coccolithophore Chrysotila roscoffensis under the effects of phosphate at high and low concentrations, and of organic phosphorus of adenosine triphosphate (ATP) and Na2-glycerophosphate (SG). The growth, photosynthesis, calcification, alkaline phosphatase activity, and inorganic nutrient absorption rate were comparatively studied. The results showed that the culture with a low concentration of initial phosphate (6 μM) had a lower growth rate than that with a high concentration (45 μM). However, a relatively similar maximum cell density could be achieved. Equimolar inorganic phosphorus supported a higher initial growth rate than organic phosphorus. ATP was better than SG at supporting higher growth rates, higher photosynthetic activity, and higher cell density. Cellular alkaline phosphatase (AP) responded rapidly to nutrient variations with sharp changes of activities, independent of the initial P resources. Cellular calcification was at a higher level in groups with lower growth rates. Phosphate in low concentration in the medium was not absorbed during the early growth period while that in high concentration was rapidly absorbed. Instead, phosphate in low concentration was rapidly absorbed in the late stationary phase. The absorption of nitrate was affected by the initial P resources as well. The DIN/DIP ratio in the water varied significantly during the growth periods. The results indicated that C. roscoffensis had flexible physiological strategies in utilizing varied phosphorus resources, and high cell density maintenance of C. roscoffensis may play roles in nutrient conditions in the water. This study may help to extend the understanding of nutrient utilization strategy in microalgae and to apply reference in the application of Chrysotila species in the removal of nutrient pollution.

Technology Selection of Microalgae Thermochemical Conversion to Bio-Crude Oil

Microalgae as a third-generation biofuel source with various advantages is a potential part of renewable energy resources. Various studies on the conversion process of microalgae into biofuels have been carried out, one of which is the thermochemical process. The thermochemical conversion process is considered better than the biochemical process which has a low conversion rate and higher production costs. Recent researches state that to obtain bio-crude oil from microalgae through a thermochemical process, there are two alternative technologies that can be used, which are pyrolysis and liquefaction. In this research, a selection was made to determine which technology was better using decision making tools of Analytic Hierarchy Process (AHP) method. The evaluation criteria that have been used are technological (readiness level, energy efficiency, pre-treatment process, and product output), operational complexity, environment, and economy (investment cost and operation cost). The alternative technologies evaluated were pyrolysis with bubbling fluidized bed reactor, pyrolysis with circulating fluidized bed reactor, and hydrothermal liquefaction. From the results of pairwise comparisons, the technological criteria had the highest weight (0.343) and hydrothermal liquefaction technology was the best alternative technology among other alternatives (0.420).

Review of recent trends and various techniques for CO2 capture: Special emphasis on biphasic amine solvents

In the present scenario, the hazardous impacts of greenhouse gases can be restricted by adopting carbon capture and storage (CCS) technology that captures most of the CO2 emitted by numerous industries, human activities, and mostly from thermal power plants. This paper reviewed the main CO2 capturing technologies, i.e., pre-combustion, post-combustion, and oxy-combustion, along with their different operating conditions, performances, and comparisons. Some industrial processes used to capture CO2 by physical solvents are presented with their properties and working conditions. Methodologies like absorption, adsorption, membrane technology, cryogenic separation, and microalgae process are presented. Single alkanolamine-based solvents have limited CO2 loading and high regeneration energy demand, attracting researchers to work on their various amine blends. In today’s scenario, biphasic solvents play a vital role in the field of CO2 capture. Some amine solvent blends show biphasic behavior, leading to faster reaction, higher absorption capacity, and lower regeneration energy. The solvent screening for the biphasic solvent is very rigorous and still challenging. In this work, various blends selected by the researchers with the potential for phase-splitting behavior are reviewed, and the best among them is reported.

Processing of marine microalgae biomass via hydrothermal liquefaction for bio-oil production: study on algae cultivation, harvesting, and process parameters

Processing of marine microalgae biomass via hydrothermal liquefaction for bio-oil production: study on algae cultivation, harvesting, and process parameters

Effect of harvesting time in the methane production on the anaerobic digestion of microalgae

ABSTRACT Microalgae are being proposed as excellent substrates for different biorefinery processes. Anaerobic digestion process of microalgae is one of these interesting processes but has some limitations in deleting cell walls. For this reason, many studies proposed different types of pre-treatments, entailing energy, operation, and investment costs. This work aims to optimize the anaerobic digestion of the microalgae Chlorella sorokiniana and Chlorella sorokiniana (strain S12/S13/S16) without any pre-treatment by selecting the optimal harvesting time. The greatest influence is seen at 5:00 PM in methane production for both microalgae. For Chlorella sorokiniana, it is the most optimal moment for anaerobic digestion, whereas Chlorella sorokiniana (strain S12/S13/S16) is the least optimal. In the other harvesting times, both microalgae present a similar methane production, i.e. 173 ± 12 mL CH4/g of total volatile solids. The highest methane production rate values were obtained during peak sunlight, 1:00 PM and 8:00 AM, respectively, and lower overnight.

ACC1 and ACC2 Genes Expression Microalgae Skletonema costatum On Stress Aeration And fotoperiode In Simultans

Abiotic stresses such as photoperiod, aeration, CO2 concentration, pH, temperature, and salinity can affect and salinity the physiological processes of microalgae. One of the physiological processes that occur is a change in the lipid biosynthetic pathway towards the formation and accumulation of neutral lipids. Neutral lipid accumulation in the form of TAGs. TAGs as one of the defense mechanisms. The regulation of fatty acid biosynthesis is initiated by the ACC1 and ACC2 genes. This study aims to determine the expression of ACC1 and ACC2 genes under conditions of aeration stress and photoperiod simultaneously in microalgae Skeletonema costatum. The method used was the analysis of gene expression in the sample of S. costatum RNA extract using qRT-PCR. Based on the results of the study, it was found that the ACC1 gene was expressed and upregulated in the A2F2 treatment (24-hour aeration and 24:0 photoperiod) with a CT value of 36.85 while the ACC2 gene was expressed and upregulated in the A1F1 treatment (12-hour aeration and 12:12 photoperiod). with the CT value of 36,874.