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.
The shape diagram reveals a clear operating region and the process limits within which spherical ca-alginate beads could be formed.
The aim of this work was to develop prediction models for shape and ...size of ca-alginate macrobeads produced through extrusion–dripping method. The relationship between the process variables on the shape and size of the alginate drops before and after gelation was established with the aid of image analysis. The results show that a critical Ohnersorge number (
Oh)
>
0.24 was required to form spherical beads. The shape transition of ca-alginate beads could be typically distinguished into three phases along the collecting distance and it was affected by the combined influence of the solution properties, the collecting distance and the drop size. Mathematical equations and a master shape diagram were developed to reveal a clear operating region and the overall process limits within which spherical ca-alginate beads could be formed. In terms of bead size, the overall size correction factor (
K) which accounted for the liquid loss factor (
k
LF
) and the shrinkage factor (
k
SF
), varied between 0.73 and 0.85 under the experimental conditions. The size prediction model correlated well with the experimental data. The approach and the outcome could be used as a model to develop prediction tools for similar bead production systems.
This study deals with the economic assessment of biodiesel production using three catalytic processes (1) alkali (2) soluble enzyme and (3) immobilized enzyme. All the processes were considered to be ...operated at batch mode with a production capacity of 103tonne. Biodiesel production cost using alkali catalyst process was found to be lowest ($ 1166.67/tonne) compared to soluble lipase catalyst ($7821.37/tonne) and immobilized lipase catalyst ($2414.63/tonne) process. The higher production cost was due to the higher cost of the enzyme and the higher reaction time of enzymatic process. However, reuse of immobilized catalyst decreased the production cost drastically unlike soluble enzyme catalyst.
The aim of this work was to determine the effect of formulation of alginate beads on their mechanical behavior and stiffness when compressed at high speed. The alginate beads were formulated using ...different types and concentrations of alginate and gelling cations and were produced using an extrusiondripping method, Single wet beads were compressed at a speed of 40 mm/min, and their elastic limits were investigated, and the corresponding force versus displacement data were obtained. The Young＇s moduli of the beads were determined from the force versus displacement data using the Hertz＇s contact mechanics theory. The alginate beads were found to exhibit plastic behavior when they were compressed beyond 50% with the exception of copper-alginate beads for which yield occured at lower deformation, Alginate beads made of higher guluronic acid contents and gelling cations of higher chemical affinity were found to have greater stiffness. Increasing the concentration of alginate and gelling ions also generated a similar effect. At such a compression speed, the values of Young＇s modulus of the beads were found to be in the range between 250 and 900 kPa depending on the bead formulation.
A comparative study on the stability and potential of alginate and pectin based beads for production of poultry probiotic cells using MRS medium in repeated batch fermentation was conducted. The bead ...cores, made of three types of materials, i.e., ca-alginate, ca-pectinate and ca-alginate/pectinate, were compared. The effect of single and double layer coatings using chitosan and core material, respectively, on the bead stability and cell production were also studied. The pectin based beads were found to be more stable than that of the alginate beads and their stability was further improved by coating with chitosan. The cell concentration in pectin based beads was comparable to that in the alginate beads. On the other hand, pectin based beads gave significantly lower cell concentration in the growth medium for the initial fermentation cycles when compared to the alginate beads. In conclusion, pectin was found to be potential encapsulation material for probiotic cell production owing to its stability and favourable microenvironment for cell growth.
A simultaneous saccharification and fermentation (SSF) optimization process was carried out on pretreated empty fruit bunches (EFBs) by employing the Response Surface Methodology (RSM). EFBs were ...treated using sequential acid-alkali pretreatment and analyzed physically by a scanning electron microscope (SEM). The findings revealed that the pretreatment had changed the morphology and the EFBs’ structure. Then, the optimum combination of enzymes and microbes for bioethanol production was screened. Results showed that the combination of S. cerevisiae and T. harzianum and enzymes (cellulase and β-glucosidase) produced the highest bioethanol concentration with 11.76 g/L and a bioethanol yield of 0.29 g/g EFB using 4% (w/v) treated EFBs at 30 °C for 72 h. Next, the central composite design (CCD) of RSM was employed to optimize the SSF parameters of fermentation time, temperature, pH, and inoculum concentration for higher yield. The analysis of optimization by CCD predicted that 9.72 g/L of bioethanol (0.46 g/g ethanol yield, 90.63% conversion efficiency) could be obtained at 72 h, 30 °C, pH 4.8, and 6.79% (v/v) of inoculum concentration using 2% (w/v) treated EFBs. Results showed that the fermentation process conducted using the optimized conditions produced 9.65 g/L of bioethanol, 0.46 g/g ethanol yield, and 89.56% conversion efficiency, which was in close proximity to the predicted CCD model.
The discrepancy of the existing literature data on the surface tension values of biopolymer solutions could be affected by the measurement technique. The aim of the study was to compare the surface ...tension values of biopolymer solutions, measured using the du Nouy ring method and the drop weight methods (Harkins–Brown correction factors method and the LCP coefficient method). Four biopolymers were chosen (sodium alginate, carboxymethyl cellulose, xanthan gum and pectin) and the surface tensions of the solutions were measured as a function of biopolymer concentration. The surface tension was found to increase with biopolymer concentration when measured using the du Nouy ring method. On the other hand, the drop weight methods gave an opposite trend. The results verified the discrepancy of the existing literature data. The error may be caused by the correction factors calculation and the solution viscosity when the du Nouy ring method was used. The LCP coefficient method which is independent of correction factors and liquid properties is proposed for measurement of the surface tension of viscous biopolymer solutions.
► Alginate solution was atomized using m˙air/m˙liq lower than 3.5. ► Ca-alginate particles with mean sizes ranging from 50 to 2300μm were produced. ► Increase in m˙air/m˙liq decreased mean particle ...size but increased size distribution. ► Particles became more spherical with an increase in m˙air/m˙liq. ► The process is easy to set up, economical and scalable.
This study investigated the effects of atomization at low air-to-liquid mass flow rate ratios m˙air/m˙liq on the size, size distribution and shape of the calcium alginate (Ca-alginate) particles produced. It was found that the m˙air/m˙liq ratio must be greater than 0.0011 to atomize a 20g/L sodium alginate solution. Ca-alginate particles with a broad mean sizes ranging from 50 to 2300μm were produced using a m˙air/m˙liq ratio lower than 3.5. The change in particle size was most significant when the m˙air/m˙liq ratio was below a critical value 0.25. An increase in the m˙air/m˙liq ratio decreased the mean particle size but increased the particle size distribution. The particles became more spherical with an increase in the m˙air/m˙liq ratio.
The validity of the existing drop weight analyses for determining surface tension could be influenced by the liquid properties. This study aimed to verify the validity of the Harkins–Brown correction ...factors and the Bond number correlation, as well as to develop a new drop weight analysis that is insensitive to liquid properties. The liquid samples of known surface tension and viscosity were chosen and classified into six different groups. Validation was done by comparing the data compiled in this study with the existing correlations as well as by dimensionless analysis. Results show that the existing drop weight analyses are valid for most liquid groups provided that the surface tension number (
N
γ
) exceeds 10
−1 or the Ohnersorge number (
Oh) is below 10
2. This, however, confirms the influence of liquid properties on the validity of the analyses. The LCP coefficient method was developed to eliminate this problem by using the drop weight results generated from multiple tips of different sizes. The surface tension could then be calculated by using a semi-empirical linear correlation. Error analysis shows that the LCP coefficient method gives the best reliability and accuracy among various drop weight analyses.
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