Preliminary study on supercritical fluid extraction of microalgae Nannochloropsis salina

Supercritical Fluid Extraction (SFE) is an emerging extraction method because it is clean, selective and efficient compared to the chemical extraction methods that use toxic solvent. Microalgae Nannochloropsis salina was selected as the feedstock in this study due to its high content of Polyunsaturated Fatty Acids (PUFA). The use of carbon dioxide (CO2) as a solvent in SFE makes the process as one of the green extraction technologies. This study aims to observe the effect of co-solvent (5% ethanol) and different types of microalgae holder (cotton and steam bun cloth) on the yield of lipid. The holder is required during the process due to the fine particle of microalgae that has potential to clog the instrument. The study was conducted for 4 hours at 60°C, 30 MPa and flow rate of 4 ml/min. The obtained lipid was then transesterified and analyzed for fatty acid methyl ester (FAME) profile. The results showed that high yield of lipid (16 wt.%) obtained when co-solvent was added during the SFE. The microalgae holder used in this study also affected the yield of lipid. The used of cotton cloth as microalgae holder for SFE with co-solvent gave high lipid yield compared to steam bun cloth. It was found that the yield of lipid from SFE was double the amount of lipid obtained using Soxhlet extraction. This preliminary findings can be further researched by optimizing the co-solvent concentration with suitable microalgae holder for high lipid yields

Preliminary study on lipid extraction from Nannochloropsis salina using supercritical carbon dioxide method

The issues involved with conventional lipid extraction methods, such as the usage of toxic solvents and accumulation of chemical waste, has motivated researchers to find an alternative approach to the extraction technology. One of the alternatives is via the Supercritical Carbon Dioxide (SC-CO2) method. This extraction method is considered as green as it provides a clean, selective and efficient process. Although the SC-CO2 method has been successfully used to extract lipids from microalgae, there are still some issues related to sample preparation and process parameters that need to be resolved. Therefore, this study investigates the effect of adding a modifier (ethanol) and using different types of holders (cotton and steam bun cloth) has on the yield of lipid from Nannochloropsis salina. The usage of a holder is required during the process due to the fine particles of the microalgae which have the potential to clog the instrument used. The SC-CO2 extraction without the modifier was conducted for 4 hours at 60°C, 30 MPa and CO2 flow rate of 4 ml/min, while the extraction with the modifier was conducted using 3.8 ml/min CO2 and 0.2 ml/min ethanol. It was found that the highest lipid yield of 0.16 g lipid / g dried microalgae was achieved using cotton cloth as a holder with the addition of the modifier. Lower amount of lipids were obtained when using the Soxhlet method (0.08 g lipid / g dried microalgae) and SC-CO2 without modification (0.02 g lipid / g dried microalgae). These preliminary findings show that the SC-CO2 process requires modifications to enhance the lipids yield from microalgae

Likelihood of using online banking services among consumers: application of logit model

Research on the area of internet banking has been extensively studied in developing countries since internet banking resumed from the new millennium. Most studies on this topic were conducted in Asian countries. Most methods adopted are attempted to analyze the ‘perception' among respondents or consumers on this technology. Very limited studies were using logit or probit regression to explore the ‘probability’ or ‘likelihood’ of consumers using internet banking, in particular among Malaysian consumers. The current study aims to analyze the probability of using digital banking services among consumers in Malaysia using survey data collected in the area of Klang Valley. Responses from the survey are analyzed empirically using logistic regression and the study finds that regardless of the choice of consumers on banks whether it is local or foreign, Islamic or conventional and regardless of how often they visit the bank(s), the likelihood of using online banking is significantly determined by the level of education they have, gender and category of employment. There is a higher probability of choosing online banking services among those who are highly educated, females and those who are not working in the government sector

A photobioreactor design for large-scale microalgae cultivation

Microalgae are a promising alternative feedstock for producing biofuels (e.g., bioethanol and biodiesel) and bio-products (e.g., omega-3 and chlorophyll). However, the high cost of developing products from microalgae remains an obstacle to the full use of microalgae. Major hindrances to the commercial viability of algae are the operational and maintenance costs associated with large-scale cultivation. Most microalga cultivation operations rely on improvised photobioreactor designs, of which open-pond systems are frequently considered for large-scale operations. A cost-effective cultivation method is needed to improve the sustainability and economics of microalga cultivation, whilst minimising space and culture contamination and maintaining the integrity of desired species. Several photobioreactor designs are reviewed for the effective cultivation of microalgae, and the advantages and limitations of these photobioreactors are highlighted. Process challenges to scaling up the design of photobioreactors for commercial operations are also discussed

Kinetic and thermodynamic characterization of amino acids generation via subcritical water reaction of microalgae Nannochloropsis sp. biomass

Emerging applications of amino acids in the development of biopharmaceuticals, functional foods and feeds, and biostimulants in sustainable agriculture have led to increasing interests in the development of commercially-viable technologies for amino acid production. Amongst the many technologies currently used, subcritical water reaction has the potential to offer a scalable and environmentally benign approach to amino acids synthesis. The present work investigates the kinetic and thermodynamic behaviour of amino acids synthesis from Nannochloropsis sp. biomass using subcritical water. Experiments were conducted in a batch reactor at temperatures between 250-280°C for a duration of 5-20 min using 1% (w/v) microalgal loading. The aqueous phase obtained from the reaction was directly analyzed for amino acid concentration. The highest amino acids yield of 0.0196 g AA / g biomass was obtained at 260°C for 20 min, representing 44% of amino acids extracted from the biomass. A single consecutive reaction model used for data validation showed a good agreement between the experimental and theoretical data generated. The results obtained from the kinetic study demonstrated that amino acids could be produced and decomposed rapidly from the subcritical water process. Thermodynamic analysis by transition-state theory showed that the subcritical water process as endothermic, while the Gibbs free energy showed the reaction as non-spontaneous, requiring constant external energy to support it

Production of amino acids from microalgae Nannochloropsis sp. biomass using subcritical water technology

The increase in the world population resulted in high demand for food, particularly proteins. Proteins are made up of long chains of amino acids. At present, animals and plants-based amino acids constitute the majority of the food that humans and livestock consume. However, due to the increase in demand, these amino acid resources will not be sufficient. Therefore, sources such as microalgae could be an alternative. Chemical synthesize and biological (enzyme and fermentation) methods are current methods to produce these amino acids. These methods used harmful chemicals, long processing steps, and high operating costs. Hence, finding a suitable amino acid production technique could significantly protect the environment, save time, and cost. This study deals with the use of the green technology approach, which is subcritical water technology. The yield and composition of amino acids produced from subcritical water of microalgae Nannochloropsis sp. were evaluated at different temperatures, time, and biomass loadings. The response surface methodology (RSM) was employed to generate empirical equations that correlate the subcritical water process parameters and the response variables, which are amino acids. The empirical equation generated was then evaluated to ensure the model adequately fit to describe and predict the production of amino acids. This study was also conducted to evaluate the kinetic and thermodynamic parameters of amino acid production from the microalgae using subcritical water technology. The results revealed the total and individual amino acids investigated produced the highest yield at different subcritical water conditions. Hence, careful selection of operating parameters (i.e., temperature, time, and biomass loading) is crucial to identify the selected amino acids when using subcritical water technology. The empirical equations obtained from RSM are inaccurate for predicting the yield of amino acids from the subcritical water of microalgae Nannochloropsis sp. biomass. However, the RSM study provides some ideas about the range of the optimum subcritical water conditions that might lead to a high yield of amino acid production. A high yield of total amino acids (1959 mg/100 g algae), leucine (134 mg/100 g algae), glycine (323 mg/100 g algae) and alanine (495 mg/100 g algae) was obtained in the kinetic study when using the optimum operating conditions, as suggested by the RSM approach. A single consecutive model used in the kinetic study is adequate to predict the production of the total amino acids, glycine, leucine and alanine at the studied temperature. The thermodynamic analysis results showed the subcritical water process as endothermic and constant energy supply needed to produce these amino acids. Overall, the findings from this study are useful to understand the production of the amino acid from microalgae Nannochloropsis sp. via the subcritical water process. Thus, the research will benefit food and pharmaceutical industries, where microalgae can be used as an alternative feedstock to meet the population's need for a more sustainable food supply, specifically concerning protein and amino acid demand

Optimization of bioethanol production from empty fruit bunches by co-culture of saccharomyces cerevisae and aspergillus niger using statistical experimental design

Production of bioethanol from oil palm empty fruit bunches (EFB) by Saccharomyces cerevisae and Aspergillus niger is among the ways of reducing environmental pollution and consumption of crude oil. This study used sequential optimization approach based on statistical experimental design including Plackett-Burman (PB) design, one-factor-at-a-time (OFAT) and face-centered central composite design (FCCCD). Among the parameters tested, pH, temperature, inoculum size, potassium dihydrogen phosphate (KH2PO4), magnesium sulphate heptahydrate (MgSO4.7H2O) and peptone showed positive effects while yeast extract, malt extract, potassium chloride, urea and agitation were influencing the production negatively. The three parameters chosen for determination of the optimum values by response surface methodology (RSM) based on the FCCCD were pH, KH2PO4 and agitation. Although agitation showed negative effects it was considered in FCCCD due to the mixing effect of fermnetation. The validity of the model was verified and the optimum value of pH 5.5, agitation of 150rpm and 0.3% of KH2PO4 led to a maximum bioethanol production of 7.4 g/l. The yield of bioethanol was determined based on the reducing sugar (16.85 g/l) obtained from the EFB

Cellulosic bioethanol production from empty fruit bunches by locally produced cellulases

The global shortage of fossil fuels and environmental concerns to reduce pollution has resuscitated the interest in bioethanol production. Bioethanol is a promising alternative energy source that can be produced from renewable resources through hydrolysis and sugar fermentation processes. Its current production mainly involves fermentation of grains rich in sugar or starch and sugarcane. However, this process is not sustainable since these raw materials are needed for food and feed production. The utilization of lignocellulosic materials for bioethanol production such as empty fruit bunches (EFB) from palm oil plant attract increasing attention as an abundantly available and cheap renewable residue especially in Malaysia where palm oil production is the major agricultural industry. Conversion of EFB to bioethanol involves a three step process. Firstly, the pretreatment of lignocellulosic material followed by hydrolysis using cellulase enzyme to produce reducing sugars and the fermentation processes in the presence of suitable microorganisms. In this study, cellulase enzyme used for the hydrolysis was produced from palm oil mill effluent (POME), whose cost of production was considerably low compared to commercial cellulases. The hydrolysis of EFB for sugar production as an initial step was statistically optimized based on agitation speed, EFB and cellulase concentrations using Response surface methodology (RSM)/ Box-Behnken design in 2L Bioreactor. Maximum sugar production was realized after three days hydrolysis. The amount of sugar produced showed an economic feasibility of using EFB as a renewable raw material for bioethanol productio

Optimization of hydrolysis process using empty fruit bunches by locally produced cellulases

The utilization of lignocellulosic materials for bioethanol production such as empty fruit bunches (EFB) from palm oil plant attract increasing attention as an abundantly available and cheap renewable residue especially in Malaysia where palm oil production is the major agricultural industry. The most challenging part in conversion of lignocellulosic materials to bioethanol is the hydrolysis process in order to obtain reducing sugar. In this study, cellulase enzyme used for the hydrolysis was produced from palm oil mill effluent (POME), whose cost of production was considerably low compared to commercial cellulases. The hydrolysis of EFB for sugar production as an initial step was statistically optimized based on agitation speed, EFB and cellulase concentrations using Response Surface Methodology (RSM)/ Box-Behnken design in 2L Bioreactor. The design contains a total of 17 experimental runs and data obtained from RSM on reducing sugar production were subjected to the analysis of variance (ANOVA) and analyzed using a second order polynomial equation. Maximum sugar production was realized after three days hydrolysis. The amount of sugar produced showed an economic feasibility of using EFB as a renewable raw material for bioethanol production