Chlorella Vulgaris FSP-E Research Articles

Upcycling food waste as a low-cost cultivation medium for Chlorella sp. microalgae.

Global food loss and waste have raised environmental concerns regarding the generation of greenhouse gases (e.g., carbon dioxide and methane gas), which directly contribute to climate change. To address these concerns, the present research aims to upcycle food waste into an alternative culture medium for the cultivation of microalgae. Various parameters including pretreatment of food waste (i.e., autoclave and non-autoclave), concentration of food waste culture medium (i.e., 10%, 30%, 50%, 70%, 90% and 100%), harvesting efficiency and biochemical compounds of Chlorella sp. microalgae were carried out. Based on the preliminary findings, the highest biomass concentration obtained from 10% food waste culture medium in the autoclave for Chlorella sp., including strains FSP-E, ESP-31 and CY-1, were 2.869 ± 0.022, 2.385 ± 0.018 and 0.985 ± 0.0026 g L-1, respectively. Since Chlorella vulgaris FSP-E exhibited the highest biomass concentration, this microalgal strain was selected to examine the subsequent parameters. Cultivation of C. vulgaris FSP-E in 100FW achieves a biomass concentration of 4.465 ± 0.008 g L-1 with biochemical compounds of 6.94 ± 1.396, 248.24 ± 0.976 and 406.23 ± 0.593 mg g-1 for lipids, carbohydrates and proteins, respectively. This study shows that using food waste as an alternative culture medium for C. vulgaris FSP-E can achieve substantial biomass productivity and biochemical content. This research work would contribute to the concept of net zero emission and transitioning toward a circular bioeconomy by upcycling food waste as an alternative culture medium for the cultivation of microalgae. © 2024 Society of Chemical Industry.

Bioethanol production from microalgae biomass at high-solids loadings

Industrial adoption of microalgae biofuel technology has always been hindered by its economic viability. To increase the feasibility of bioethanol production from microalgae, fermentation was applied to Chlorella vulgaris FSP-E biomass at high-solids loading conditions. First, Chlorella vulgaris FSP-E was cultivated to produce microalgae biomass with high carbohydrate content. Next, different ethanol-producing microorganisms were screened. Saccharomyces cerevisiae FAY-1 showed no inhibition when fermenting high initial glucose concentrations and was selected for the fermentation experiments at high-solids loadings. Optimization of acid hydrolysis at high biomass loading was also performed. The fermentation of microalgal biomass hydrolysate produced a final ethanol concentration and yield higher than most reported literature using microalgae feedstock. In addition, the kinetics of bioethanol fermentation of microalgae hydrolysate under high-solids loading were evaluated. These results showed the potential of fermenting microalgae biomass at high-solids loading in improving the viability of microalgae bioethanol production.

Catalytic microwave torrefaction of microalga Chlorella vulgaris FSP-E with magnesium oxide optimized via taguchi approach: A thermo-energetic analysis

Biochar is a promising material and fuel for environmental sustainability. Microalgal biochar is produced using catalytic microwave torrefaction of Chlorella vulgaris FSP-E residue with magnesium oxide as a microwave absorber to enhance heating. Using Taguchi experimental design (TED) and Analysis of Variance (ANOVA), the effects of microwave power, catalyst concentration, and duration on energy yield are investigated. Both TED and ANOVA confirm the significant effects of microwave power and catalyst concentration, while only a slight effect from duration. The calorific values of produced biochar (21.12–26.22 MJ⋅kg−1) are close to coal. The maximum deoxygenation and carbonization extents are 56.69% and 35.23%, respectively. The optimal parameter combination of low microwave power (450 W), low duration (25 min), and high catalyst concentration (10 wt% MgO) poses the highest upgrading energy index (UEI) value. This confirms that better energy efficiency leans towards light torrefaction conditions with maximized catalyst concentration to produce the maximum energy yield while consuming the least electricity input.

Chlorella vulgaris FSP-E cultivation in waste molasses: Photo-to-property estimation by artificial intelligence

This progress of industry revolution, which involves reutilizing waste materials and simplifying complex procedures of analysis through artificial intelligent (AI), are the current interest in automated industries. There are two main objectives, firstly, the use of waste molasses from sugar mills as a cultivation medium for microalgae and nutrients extraction. The biomass in 15% of the molasses medium without carbon dioxide aeration during cultivation obtained the highest dry cell weight at 1206.43 mg/L. Protein content in the biomass of 10% molasses cultivation medium is 20.60%, which is higher compared to commercial mediums. Secondly, the exploitation of the deep colouration properties of molasses-cultivated microalgae, a novel photo-to-property estimation was performed by k-Nearest Neighbour (k-NN) algorithm through RGB model pixel raster in the images to rapidly determine the biomass concentration, nitrogen concentration and pH without use of tedious analytical processes. The k-value at 4 was studied in normalized Root-Mean-Square-Error (RMSE) for biomass concentration at 0.10, nitrate at 0.11, and pH at 0.02 for a sequence of days.

Microalgal Protein Extraction From Chlorella vulgaris FSP-E Using Triphasic Partitioning Technique With Sonication.

Green microalgae containing various bioactive compounds and macronutrients such as lipids, carbohydrates, and proteins, have attracted much attention from the global community. Microalgae has the potential to be applied in food industries due to its high protein content, rapid growth rate, and ability to survive in harsh conditions. This study presents a simple yet efficient technique of sonication-assisted triphasic partitioning process, also known as ultrasonic-assisted three phase partitioning (UATPP), for the extraction of proteins from Chlorella vulgaris FSP-E. Comparison studies between three phase partitioning (TPP) and UATPP was conducted to investigate the feasibility of the enhanced technique on proteins extraction. Types of salt, ratio of slurry to t-butanol, salt saturation, sonication frequency, power, irradiation time, and duty cycle as well as biomass loading were studied. UATPP was found to be an improved technique compared to TPP. An optimum separation efficiency and yield of 74.59 ± 0.45 and 56.57 ± 3.70% was obtained, respectively, with the optimized conditions: salt saturation (50%), slurry to t-butanol ratio (1:2), sonication power (100%), irradiation time (10 min), frequency (35 kHz), duty cycle (80%) and biomass loading (0.75 wt%). A scaled-up study was performed to validate the reliability of UATPP for protein extraction. The outcome of the study revealed that UATPP is an attractive approach for downstream processing of microalgae.

Development of CRISPR/Cas9 system in Chlorella vulgaris FSP-E to enhance lipid accumulation

Microalgae biorefinery is an alternative, sustainable and promising trend to solve the problem of fossil oil depletion and carbon dioxide emission. However, considering the innate limitation of cell growth and oil content in microalgae, to accelerate metabolic balance by CRISPR/Cas9 system is attractive. At first, plasmid based from Agrobacterium tumefaciens and a fragment of mGFP was transformed into Chlorella sorokiniana and Chlorella vulgaris FSP-E by electroporation, respectively. Selected colonies were tested by spectrophotometer and inverted fluorescence microscopy (IFM), and an increase of fluorescent was observed by 67% compared with that in wild type, which proved the Agrobacterium-mediated plasmid is suitable for gene insertion in Chlorella species. Consequently, plasmid with similar structure as mentioned previously containing fragment of Cas9 with sgRNA designed on omega-3 fatty acid desaturase (fad3) gene was constructed and showed a higher accumulation of lipid content by 46% (w/w) in C. vulgaris FSP-E. This is first-time to use CRISPR/Cas9 based technology for gene manipulation in Chlorella.

Optimization of protein extraction from Chlorella Vulgaris via novel sugaring-out assisted liquid biphasic electric flotation system.

Microalgae biomass has been consumed as animal feed, fish feed and in human diet due to its high nutritional value. In this experiment, microalgae specie of Chlorella Vulgaris FSP-E was utilized for protein extraction via simple sugaring-out assisted liquid biphasic electric flotation system. The external electric force provided to the two-phase system assists in disruption of rigid microalgae cell wall and releases the contents of microalgae cell. This experiment manipulates various parameters to optimize the set-up. The liquid biphasic electric flotation set-up is compared with a control liquid biphasic flotation experiment without the electric field supply. The optimized separation efficiency of the liquid biphasic electric flotation system was 73.999±0.739% and protein recovery of 69.665±0.862% compared with liquid biphasic flotation, the separation efficiency was 61.584±0.360% and protein recovery was 48.779±0.480%. The separation efficiency and protein recovery for 5 × time scaled-up system was observed at 52.871±1.236% and 73.294±0.701%. The integration of simultaneous cell-disruption and protein extraction ensures high yield of protein from microalgae. This integrated method for protein extraction from microalgae demonstrated its potential and further research can lead this technology to commercialization.

Towards protein production and application by using Chlorella species as circular economy

In this study, productions of microalgal proteins were explored via a circular economy concept. First, production of proteins from Chlorella vulgaris FSP-E (CV) and Chlorella sorokiniana (CS) was optimized by using favorable cultivation conditions and strategies. The optimal CO2 concentration for the growth of both microalgae was 5% (v/v), while the optimal nitrogen source for CV and CS were 12 mM of NaNO3 and NH4Cl, respectively. Addition of 12 mg/L ammonium iron (III) citrate enhanced protein production. Next, semi-batch cultivation strategy was employed to achieve a protein production of 793.3 and 812.8 mg/L for CV and C S, representing a 4.86 and 2.77 fold increase, respectively, in protein productivity. The obtained microalgal proteins consist of 40% essential amino acids. The CV and CS proteins possess prebiotic activities as they enhanced the growth of Lactobacillus rhamnosus ZY by 48 and 74%, respectively, with a good antibacterial activity against predominant pathogens.

Biochar production from microalgae cultivation through pyrolysis as a sustainable carbon sequestration and biorefinery approach

Microalgae cultivation and biomass to biochar conversion is a potential approach for global carbon sequestration in microalgal biorefinery. Excessive atmospheric carbon dioxide (CO2) is utilized in microalgal biomass cultivation for biochar production. In the current study, microalgal biomass productivity was determined using different CO2 concentrations for biochar production, and the physicochemical properties of microalgal biochar were characterized to determine its potential applications for carbon sequestration and biorefinery. The indigenous microalga Chlorella vulgaris FSP-E was cultivated in photobioreactors under controlled environment with different CO2 gas concentrations as the sole carbon source. Microalgal biomass pyrolysis was performed thereafter in a fixed-bed reactor to produce biochar and other coproducts. C. vulgaris FSP-E showed a maximum biomass productivity of 0.87 g L−1 day−1. A biochar yield of 26.9% was obtained from pyrolysis under an optimum temperature of 500 °C at a heating rate of 10 °C min−1. C. vulgaris FSP-E biochar showed an alkaline pH value of 8.1 with H/C and O/C atomic ratios beneficial for carbon sequestration and soil application. The potential use of microalgal biochar as an alternative coal was also demonstrated by the increased heating value of 23.42 MJ kg−1. C. vulgaris FSP-E biochar exhibited a surface morphology, thereby suggesting its applicability as a bio-adsorbent. The cultivation of microalgae C. vulgaris FSP-E and the production of its respective biochar is a potential approach as clean technology for carbon sequestration and microalgal biorefinery toward a sustainable environment.

Outdoor cultivation of Chlorella vulgaris FSP-E in vertical tubular-type photobioreactors for microalgal protein production

Aquafeeds rely heavily on fishmeal as the major protein source. However, the recent increase in the price of fishmeal and sharp decrease in fish resources have resulted in a major threat to the aquaculture industry. Therefore, cost-effective and sustainable fishmeal alternatives should be found. While microalgae are considered a promising alternative to fishmeal, the cultivation scale should be enlarged and its protein production cost should be much lower. In this study, Chlorella vulgaris FSP-E was grown in 50-liter outdoor photobioreactors (PBRs) to produce microalgal proteins. Using the optimum urea concentration (18.6mM), inoculum size (0.2g/L) and aeration rate (0.05vvm), the maximum biomass productivity (268.1mg/L/d) and protein productivity (155.4mg/L/d) were obtained. Semi-batch operation with a 50% medium replacement ratio attained a high protein content and productivity of 52.2% and 125.2mg/L/d, respectively. The resulting microalgal protein contained 60.3% indispensable amino acids, thus possessing a high commercial value.

Producing carbohydrate-rich microalgal biomass grown under mixotrophic conditions as feedstock for biohydrogen production

Three indigenous microalgae strains (Scenedesmus subspicatus GY-16, Chlorella vulgaris FSP-E, and Anistrodesmus gracilis GY-09) were evaluated for their ability to accumulate carbohydrates to subsequently serve as feedstock for biohydrogen production. The results of photoautotrophic growth show that among the three strains examined, C. vulgaris FSP-E displayed the highest biomass productivity (825.6 mg/L/d) and carbohydrate productivity (365.8 mg/L/d). Mixotrophic growth of C. vulgaris FSP-E with the addition of 2.0 g/l of sodium acetate further increased the biomass and carbohydrate productivity to 1022.3 mg/L/d and 498.5 mg/L/d, respectively. Moreover, operating photobioreactor on semi-batch mode enhanced the stability for prolonged incubation of the carbohydrate-rich C. vulgaris FSP-E and the biomass and carbohydrate productivity obtained were 1063.3 and 384.8 mg/L/d, respectively. The biomass of C. vulgaris FSP-E was then used as feedstock for biohydrogen production via separate hydrolysis and fermentation processes. The acidic hydrolysate (hydrolyzed with 1% H2SO4) was fermented with Clostridium butyricum CGS5, giving a maximum H2 yield of 2.87 mmol H2/g biomass and a H2 production rate of 176.9 ml/h/l, which are higher than most reported values. The results obtained in this work indicate that carbohydrate-based microalgae feedstock shows good potential for biohydrogen production.

Improving protein production of indigenous microalga Chlorella vulgaris FSP-E by photobioreactor design and cultivation strategies.

Fish meal is currently the major protein source for commercial aquaculture feed. Due to its unstable supply and increasing price, fish meal is becoming more expensive and its availability is expected to face significant challenges in the near future. Therefore, feasible alternatives to fish meal are urgently required. Microalgae have been recognized as the most promising candidates to replace fish meal because the protein composition of microalgae is similar to fish meal and the supply of microalgae-based proteins is sustainable. In this study, an indigenous microalga (Chlorella vulgaris FSP-E) with high protein content was selected, and its feasibility as an aquaculture protein source was explored. An innovative photobioreactor (PBR) utilizing cold cathode fluorescent lamps as an internal light source was designed to cultivate the FSP-E strain for protein production. This PBR could achieve a maximum biomass and protein productivity of 699 and 365 mg/L/day, respectively, under an optimum urea and iron concentration of 12.4 mM and 90 μM, respectively. In addition, amino acid analysis of the microalgal protein showed that up to 70% of the proteins in this microalgal strain consist of indispensable amino acids. Thus, C. vulgaris FSP-E appears to be a viable alternative protein source for the aquaculture industry.

Enhancing Biohydrogen Production from Chlorella Vulgaris FSP-E Under Mixotrophic Cultivation Conditions

In this study, three indigenous microalgae strains (Scenedesmus subspicatus GY-16, Chlorella vulgaris FSP-E, and Anistrodesmus gracilis GY-09) were evaluated for their performance on producing carbohydrates, which serve as feedstock for bioH2 production. The results show that C. vulgaris FSP-E displayed the highest growth rate (825.6mg/L/d) and carbohydrate productivity (365.8mg/L/d). Different sodium acetate concentrations were supplemented into the growth medium to investigate the effect of organic carbon source on biomass and carbohydrate productivity. The results show that using 2000mg/l sodium acetate to grow C. vulgaris FSP-E resulted in the highest biomass and carbohydrate productivity of 1022.3mg/l/d and 498.5mg/l/d, respectively. Meanwhile, to assess the practical applicability of the proposed microalgae-based carbohydrates production system, the photobioreactor was further operated on semi-batch mode for a prolonged incubation time under the optimal conditions. The results show that the biomass and carbohydrate productivity of C. vulgaris FSP-E was stably maintained at 1173.6 and 371.4mg/L/d, respectively. Due to the high carbohydrate content, C. vulgaris FSP-E is considered an excellent feedstock for biohydrogen fermentation. Using the acidic hydrolysate of C. vulgaris FSP-E as feedstock, the separate hydrolysis and fermentation (SHF) process could achieve high-yield hydrogen production with a maximum hydrogen yield of 2.67g hydrogen/g microalgae biomass, which is higher than most reported values. These results indicate that using carbohydrate-rich microalgae as feedstock to produce biohydrogen is indeed feasible for practical applications.

Characterization and optimization of carbohydrate production from an indigenous microalga Chlorella vulgaris FSP-E

In this study, three indigenous microalgae isolates were examined for their ability to produce carbohydrates. Among them, Chlorella vulgaris FSP-E displayed relatively high cell growth rate and carbohydrate content. The carbohydrate productivity of C. vulgaris FSP-E was further improved by using engineering strategies. The results show that using an appropriate light intensity and inoculum size could effectively promote cell growth and carbohydrate productivity. Nitrogen starvation triggered the accumulation of carbohydrates in the microalga, achieving a carbohydrate content of 51.3% after 4-day starvation. Under the optimal conditions, the highest biomass and carbohydrate productivity were 1.437 and 0.631gL−1d−1, respectively. This performance is better than that reported in most related studies. Since glucose accounted for nearly 93% of the carbohydrates accumulated in C. vulgaris FSP-E, the microalga is an excellent feedstock for bioethanol fermentation.

Bioethanol production using carbohydrate-rich microalgae biomass as feedstock

This study aimed to evaluate the potential of using a carbohydrate-rich microalga Chlorella vulgaris FSP-E as feedstock for bioethanol production via various hydrolysis strategies and fermentation processes. Enzymatic hydrolysis of C. vulgaris FSP-E biomass (containing 51% carbohydrate per dry weight) gave a glucose yield of 90.4% (or 0.461g (gbiomass)−1). The SHF and SSF processes converted the enzymatic microalgae hydrolysate into ethanol with a 79.9% and 92.3% theoretical yield, respectively. Dilute acidic hydrolysis with 1% sulfuric acid was also very effective in saccharifying C. vulgaris FSP-E biomass, achieving a glucose yield of nearly 93.6% from the microalgal carbohydrates at a starting biomass concentration of 50gL−1. Using the acidic hydrolysate of C. vulgaris FSP-E biomass as feedstock, the SHF process produced ethanol at a concentration of 11.7gL−1 and an 87.6% theoretical yield. These findings indicate the feasibility of using carbohydrate-producing microalgae as feedstock for fermentative bioethanol production.