The current issues of the depletion of fossil fuels reserve and environmental changes have increased the concern for the hunt of sustainable renewable energy for the future generations. Biofuels ...emerged as a promising viable alternative to replace the existing fossil fuels. Among these, bioethanol outstands due to its ability to substitute gasoline. However, the major challenge in bioethanol industry is the need to discover a suitable feedstock together with an environmentally friendly approach and an economically feasible process of production. The first generation and second generation bioethanol appeared unsustainable due to its impact on food security as well as inflated production process. These problems and concerns have directed the search for the third generation bioethanol (TGB) feedstock from marine algae. The integration of algae (microalgae and macroalgae) as a sustainable feedstock for bioethanol has gained worldwide attention in terms of food security and environmental impact. The research on algal utilization in bioethanol has increased in recent years and is expected to become the major drives in bioethanol industry. Therefore, the potential and prospects of the third generation bioethanol feedstock are being highlighted in this review. An insight into the current hydrolysis and fermentation technologies on algal conversion together with the economics and viability of the process are also accounted. This review can be crucial in providing ideas for the future studies that can be implemented in the commercialization of bioethanol from the third generation feedstock.
Bioethanol has been identified as the mostly used biofuel worldwide since it significantly contributes to the reduction of crude oil consumption and environmental pollution. It can be produced from ...various types of feedstocks such as sucrose, starch, lignocellulosic and algal biomass through fermentation process by microorganisms. Compared to other types of microoganisms, yeasts especially
is the common microbes employed in ethanol production due to its high ethanol productivity, high ethanol tolerance and ability of fermenting wide range of sugars. However, there are some challenges in yeast fermentation which inhibit ethanol production such as high temperature, high ethanol concentration and the ability to ferment pentose sugars. Various types of yeast strains have been used in fermentation for ethanol production including hybrid, recombinant and wild-type yeasts. Yeasts can directly ferment simple sugars into ethanol while other type of feedstocks must be converted to fermentable sugars before it can be fermented to ethanol. The common processes involves in ethanol production are pretreatment, hydrolysis and fermentation. Production of bioethanol during fermentation depends on several factors such as temperature, sugar concentration, pH, fermentation time, agitation rate, and inoculum size. The efficiency and productivity of ethanol can be enhanced by immobilizing the yeast cells. This review highlights the different types of yeast strains, fermentation process, factors affecting bioethanol production and immobilization of yeasts for better bioethanol production.
Bioethanol has been emerging from different types of renewable feedstocks as an alternative to reduce problems caused by the use of fossil fuels. Galactose is the major sugar obtained from the ...hydrolysis of seaweeds and can be fermented to ethanol by yeast. Wild-type Saccharomyces cerevisiae has been reported with good performance of galactose fermentation. The first part of the study focused on the isolation and characterization of wild-type S. cerevisiae with the ability to ferment galactose to ethanol. A wild-type S. cerevisiae strain with the ability to ferment galactose to ethanol was isolated from grape with ethanol tolerance of 15%. Immobilization of yeast cells has been performed to increase the ethanol production. The second part of the study involved the immobilization of the isolated wild-type S. cerevisiae in PVA-alginate beads. Batch fermentation of galactose by immobilized wild-type S. cerevisiae obtained ethanol concentration and yield efficiency of 9.57 g/L and 93.82%. The immobilized wild-type S. cerevisiae were used for four cycles of galactose fermentation and obtained ethanol concentration of 7.66 g/L with yeast relative activity of 79.07%. In short, bioethanol produced by galactose fermenting wild-type S. cerevisiae can be a future sustainable fuel.
•Wild-type galactose fermenting S. cerevisiae was isolated from grape.•It was successfully immobilized in PVA-alginate beads.•It showed high efficiency of fermenting galactose to ethanol.
The effect of CeO2 addition ranging from 0 wt. % to 7 wt. % on phase, microstructural evolution, physical and mechanical properties of ZTA-3 wt. % TiO2 ceramic composite were investigated. The ...samples were prepared by solid-state mixing and sintered at 1600 °C for 1hr under pressureless condition. Samples were then characterized by XRD, SEM, densitometer and Vickers indentation method. Based on XRD analysis, m-ZrO2 began to diminish at 1 wt.% CeO2 while secondary phases, i.e. Ce0.7Zr0.3O2and Zr0.4Ti0.6O2 initiated at 3 wt.% CeO2 addition. SEM images showed finer grain sizes was produced upon increasing amount of CeO2 up to 5 wt.%, corresponding to higher average grain intercept (AGI) values. From the results obtained, the optimum amount of CeO2 addition was at 5 wt. % which yielded the highest bulk density (4.41 g/cm3), firing shrinkage (21.94%), hardness (1580.10HV) and fracture toughness (9.77 MPa m1/2). This is contributed by the grain refinement and the highest amount of secondary phases formed, especially Zr0.4Ti0.6O2. However, with an excessive addition of CeO2, i.e more than 5 wt.%, grain sizes enlarged and the amount of secondary phases reduced, which degraded the mechanical properties of ZTA-3 wt. % TiO2.
•Effects of CeO2 addition on the ZTA-TiO2 systems were investigated.•Small additions of CeO2 lead to improved mechanical properties.•Effects of excessive amount of CeO2 addition have been discussed.
This study investigated the performance of hydrophobic surface treatment by using silica aerogel powder via spray coating techniques. Hydrophobic properties were determined by measuring the level of ...the contact angle. Meanwhile, performance was evaluated in term of the hydrogen gas flow and humidity rejection. The results are shown by contact angle that the microstructure filter, especially in the upper layer and sub-layer has been changed. The results also show an increase of hydrophobicity due to the increased quantity of silica aerogel powder. Results also showed that the absorption and rejection filter performance filter has increased after the addition of silica aerogel powder. The results showed that with the addition of 5 grams of powder of silica aerogel have the highest result of wetting angle 134.11°. The highest humidity rejection found with 5 grams of powder of silica aerogel.
This study was conducted to investigate the effect of solvent concentration on the performance of polysulfone membrane via airbrush spray method. The solvent concentration was varied from 73% to 80% ...in dope solution. The study also investigated airbrush processing parameter such as spray time and distance at different solvent concentration. The prepared membrane was characterized in respect to its morphology and the performance of the membrane were evaluated via gas permeability performance. This study found that the membrane fiber size was reduced as solvent concentration increases. When time increased the diameter of fiber also increased. The distance also affected the fiber size, when the distance increased the diameter of fiber became smaller. 80% of solvent concentration has better filtration and separation ability compared to other solvent due to its porosity and morphology. From the gas permeability cell testing it shows that the permeability is increasing as the solvent concentration decrease.
This study investigated the effect of the hydrophobic surface treatment effect of air filter performance by using silica aerogel powder as an additive by using spray coating techniques. The membrane ...characterization tests were carried out on a filter prepared from different additive concentration. Studies on the cross-section and the distribution of particles on the membrane were carried out using a scanning electron microscope (SEM), and the surface morphology was investigated by x-ray spectroscopy (EDS). The results are shown by SEM and EDS that the microstructure filter, especially in the upper layer and sub-layer has been changed. The results also show an increase of hydrophobicity due to the increased quantity of silica aerogel powder.
The effect of CeO2 addition ranging from 0 wt. % to 7 wt. % on phase, microstructural evolution, physical and mechanical properties of ZTA-3 wt. % TiO2 ceramic composite were investigated. The ...samples were prepared by solid-state mixing and sintered at 1600 °C for 1hr under pressureless condition. Samples were then characterized by XRD, SEM, densitometer and Vickers indentation method. Based on XRD analysis, m-ZrO2 began to diminish at 1 wt.% CeO2 while secondary phases, i.e. Ce0.7Zr0.3O2and Zr0.4Ti0.6O2 initiated at 3 wt.% CeO2 addition. SEM images showed finer grain sizes was produced upon increasing amount of CeO2 up to 5 wt.%, corresponding to higher average grain intercept (AGI) values. From the results obtained, the optimum amount of CeO2 addition was at 5 wt. % which yielded the highest bulk density (4.41 g/cm3), firing shrinkage (21.94%), hardness (1580.10HV) and fracture toughness (9.77 MPa m1/2). This is contributed by the grain refinement and the highest amount of secondary phases formed, especially Zr0.4Ti0.6O2. However, with an excessive addition of CeO2, i.e more than 5 wt.%, grain sizes enlarged and the amount of secondary phases reduced, which degraded the mechanical properties of ZTA-3 wt. % TiO2.
Anaerobic digestion has been proven as sustainable process technology for organic waste conversion into renewable bio-energy. This study was conducted to evaluate the performance of mono-digestion ...process for different types of food waste substrates using pilot scale anaerobic bio-digester (1200 L) in terms of biogas production and the chemical oxygen demand (COD) removal efficiency. The biochemical methane potential (BMP) test of rice waste (R), vegetable waste (VW) and coconut meat residue (CMR) were tested at initial volatile solid (VS) loading of 0.1631, 1.1690, 1.0059 g VS/L, respectively at fixed inoculum/substrate (I/S) ratio of 0.5. Further study conducted by using rice waste (R) in pilot plant anaerobic bio-digester (1200L) for 43 days to investigate the reactor performance in term of COD removal efficiency. Interestingly, inoculum used for this study performs very well and able to digest food waste. Results demonstrate that the maximum specific biogas yield (SBY) was observed from rice waste (R) at 0.0587 L/kg VS compared to other substrates. Specific biogas yield (SBY) of rice waste (R) was 16.01% and 11.92% higher than substrate vegetable waste (VW) and coconut meat residue (CMR) respectively. High COD removal efficiency of pilot plant bio-digester (up to 93 %) using rice waste (R) as sole substrate indicates a good performance of reactor in treating food waste. Conversion of food waste to biogas in pilot plant bio-digester is highly potential as one of the sustainable waste treatment technology.
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