Pakawadee Kaewkannetra

The effect of CO2 and salinity on the cultivation of Scenedesmus obliquus for biodiesel production

Biodiesel is a renewable and environmental friendly energy source that can be produced via tranesterification from various oil crops such as soy bean, sunflower, palm, and algae. In this work, the microalgae Scenedesmus obliquus, S. armatus and S. bernadii, isolated from natural water basins, were enriched in modified Chu 13 medium. Only S. obliquus showed significant oil accumulation and was thus further cultivated in 3 L tubular photo-reactors under mixotrophic conditions (16:8 h light-dark cycle) at room temperature and varying CO2 (5, 10, and 15%) supply. The results indicated that S. obliquus can be grown under various CO2 concentrations. A maximum biomass of 2.3 g/L was achieved when 15% CO2 was used. The effect of salinity on oil storage was also considered, using sodium chloride (NaCl) solutions of varying concentrations (0.05, 0.2, and 0.3 M). Higher lipid contents were found in cells that were subjected to salt stress compared to those in conditions without salt stress. A maximum oil accumulation of 36% was observed within 15 days at 0.3 M NaCl. A biodiesel yield of up to 97.4% was obtained.

Cyanide removal from cassava mill wastewater using Azotobactor vinelandii TISTR 1094 with mixed microorganisms in activated sludge treatment system

Cassava mill wastewater has a high organic and cyanide content and is an important economic product of traditional and rural low technology agro-industry in many parts of the world. However, the wastewater is toxic and can pose serious threat to the environment and aquatic life in the receiving waters. The ability of Azotobactor vinelandii TISTR 1094, a N2-fixing bacterium, to grow and remove cyanide in cassava wastewater was evaluated. Results revealed that the cells in the exponential phase reduce the level of cyanide more rapidly than when the cells are at their stationary growth phase. The rate of cyanide removal by A. vinelandii depends on the initial cyanide concentration. As the initial cyanide concentration increased, removal rate increased and cyanide removal of up to 65.3% was achieved. In the subsequent pilot scale trial involving an activated sludge system, the introduction of A. vinelandii into the system resulted in cyanide removals of up to 90%. This represented an improvement of 20% when compared to the activated sludge system which did not incorporate the strain.

Cost-effective defined medium for the production of polyhydroxyalkanoates using agricultural raw materials.

According to the cost of carbon substrate for producing biopolymer of polyhydroxyalkanoates (PHAs) still has a barrier to extend in an industrial scale. The aim of this work was to evaluate the defined PHAs media containing the agricultural raw materials of pineapple and sugarcane to produce PHAs by Bacillus strain. Batch fermentation was carried out in flask scale to compare the efficiency of defined media using statistical methodology. The defined medium 8 of pineapple was achieved the highest PHAs concentration and productivity (1.86 g/L and 0.077 g/Lh). The effect of pH and aeration was extensively studied in a fermentor. The results were revealed that PHAs production would be increased from the condition of uncontrolled pH and at higher aeration rate. The extracted PHAs clearly showed in a homopolymer structure of poly(3-hydroxybutyrate) (PHB) with melting temperature (Tm) of 172°C 54.39% crystallinity.

An alternative approach to the fermentation of sweet sorghum juice into biopolymer of poly- β -hydroxyalkanoates (PHAs) by newly isolated, Bacillus aryabhattai PKV01

This work revealed for the first time the possible use of a newly isolated Bacillus aryabhattai PKV01 for poly-β-hydroxyalkanoates (PHAs) production from fermentative sweet sorghum juice. Its growth and PHA production were investigated under different pH and nitrogen sources. Medium composition was optimized using statistical tools. The highest biomass and PHA content were reached at pH 6.5 with the use of urea. Plackett-Burman design was then applied to test the relative importance of medium components and process variables on cell growth and PHA production. Cell growth and PHAs production were affected by total sugar and urea and were subjected to optimize the sorghum juice medium using response surface methodology (RSM) via central composite design (CCD). The predicted optimal culture composition was achieved. Maximum dry cell weight and PHAs were obtained using a flask and almost double the amount was achieved using a bioreactor. After PHA recovery, the structure and thermal properties were characterised and revealed to be similar to the standard of poly-β-hydroxybutyrate (PHB).

Experimental study and cost evaluation for ethanol separation from fermentation broth using pervaporation.

Abstract In this work, the separation of two types of mixtures, ethanol–water mixture and fermented sweet sorghum, was investigated using cellulose acetate supported polyvinyl alcohol composite membranes. The pervaporation (PV) performances of the two mixtures under different operating parameters (ethanol concentrations, operating times and temperatures) were studied. PV performances using sweet sorghum fermentation broth, under all operating parameters, were significantly lower compared to separating ethanol from binary mixtures. Preliminary economic analysis shows that cost of producing 1 l of ethanol from the broth is about 0.9

Bioleaching of zinc from gold ores using Acidithiobacillus ferrooxidans

/l which is about 1.1 times higher than from the pure binary system.

Fabrication of Novel Polyhydroxybutyrate-co-Hydroxyvalerate (PHBV) Mixed with Natural Rubber Latex

The present work investigated microbial leaching of zinc from ore using Acidithiobacillus ferrooxidans (ATCC 14859). The ore samples, consisted of 13wt% zinc, were obtained from a gold mine in north-eastern Thailand. A shake flask study was performed on the ore samples using a rotary shaker under the following fixed conditions (250 r•min^(-1), 30°C for 16 d). The influence of various conditions, namely medium type (with and without iron), particle ore size (＜20, 20-40, 40-60, 60-100, and ＞100 mesh), ore density (20 kg•m^(-3), 50 kg•m^(-3), and 100 kg•m^(-3)), and pH of the medium (2, 2.5, 2.8, and 3), were investigated. The microbial leaching was assessed by determining the concentration of zinc in the medium and compared with the initial sample concentration. The results show that Acidithiobacillus ferrooxidans can successfully leach zinc by as much as 6 times compared with the control experiment (without Acidithiobacillus ferrooxidans ferrooxidans). The maximum efficiency (92.3%) for microbial leaching is obtained in iron-containing medium, 20-40 mesh ore sizes, 20 kg•m^(-3) ore density at pH 2.8, and the zinc content is found in the medium at about 120 mg•L^(-1).

Quality Improvement and Characteristics of Polyhydroxyalkanoates (PHAs) and Natural Latex Rubber Blends

Polyhydroxybutyrate-co-hydroxyvalerate (PHBV) is mixed with natural rubber latex to make better mechanical properties of PHBV. The various ratios between PHBV and natural rubber latex are examined to improve their mechanical properties. The PHBV are solid, easily broken, while natural rubber is excessive elastic materials. Concentrations of the employed PHBV solution are 1, 2, and 3 (%w/v). The mixtures of this solution to natural rubber latex are fabricated the biofilms in three different ratios, 4:6, 5:5, and 6:4, respectively. The films are characterized by electron microscope, universal testing machine, and differential scanning calorimetry (DSC). The electron micrographs of the mixed films and unmixed PHBV yield the lowest void distributions in 3%w/v PHBV. For mechanical properties, the averaged elastic moduli of 1, 2, and 3 (%w/v PHBV) mixed films are 773, 955 and 1,008 kPa, respectively. Their tensile strengths increase with increasing the PHBV concentrations. A similar trend is also found in elastic modulus. The crystallization and melting behavior of pure PHBV and the mixed films are examined by DSC. Melting transition temperatures of pure PHBV exhibit two melting peaks at 154°C and 173°C. In addition, the melting peaks of the mixed films remain in the range of 152-156°C and 168-171°C, respectively. According to their morphology, void distributions reduce twice, compared to the unmixed PHBV. Mechanical properties and thermal analysis indicate that the mixed PHBV can be improved their properties with more resilient and wide range temperature than usual.

Microstructural Evolution of Synthesized Polyhydroxyalkanoates (PHAs) Corresponding to their Blends

Biopolymers of hard, brittle and low flexible polyhydroxyalkanoates (PHAs) and a soft and high elastic natural-latex rubber are blended at room temperature by using a combination technique. Concentrations of the PHAs solution are constituted at 1%, 2% and 3% w/v and mingled with fresh natural latex in different ratios (PHAs : Latex Rubber = 0:10, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1 and 10:0). After vigorous blending, forming polymeric sheets leave a dried-film pattern. Only the best 3 different ratios (4:6, 5:5 and 6:4) are selected by evaluating morphological-based information. These lead to actually define and characterize for their morphological and mechanical properties. The morphological attributes are exemplified by polarized optical microscopy and X-ray diffractometry (XRD) while the thermal characterization is determined by differential scanning calorimetry (DSC). Morphological analysis for the criterion of blending achievement indicated that there is a significant relationship among porosity, texture and shrinkage. The porosity shows obviously low to high for gradually increasing PHAs and decreasing the latex. Thus, dense texture and shrinkage relate to blending compositions between PHAs and latex. The XRD and DSC reveal certain aspects of decreasing crystallinity arising from enhancing of the latex content. A high degree of crystallinity and melting temperature relates to greater PHAs ratio. The mechanical investigations have revealed complex localization patterns of tensile strength and elastic modulus. The more PHAs concentration at 2% w/v indicates the greater elastic modulus than 3% and 1% w/v. Significant differences are found on polymeric composites of mechanical analyses between PHAs and natural latex. The constituted superiority in the ratio of 5:5 significantly differs in extension to break. Additionally, both tensile strength and elastic modulus of 2% w/v PHAs present the maximum value among them.

H2-Assisted Chemical Reaction for Green-Kerosene Production

Biopolymers of polyhydroxyalkanoates (PHAs) are produced by pure bacterial strain of Alcaligenes eutrophus TISTR 1095 via batch fermentation using sugarcane juice as a carbon source, and yielded up to 21% (w/w) after recovery process. The PHAs are blended with bio-based materials such as tapioca and corn starch including glycerol and methanol to improve their microstructures. The combination of various plasticizers with PHAs is studied in different ratios. The PHAs and starch are mixed for 3% w/v and 30% w/v in hot chloroform, respectively. The varieties of PHAs to starch solution ratios are situated for casting as of films. The PHAs blended films are characterized by polarized light microscopy, differential scanning calorimetry (DSC) and x-ray diffractometry (XRD). The initial PHAs indicate remarkably crystalline structure with cross-polarized light on optical microscope. Macroscopic scales of their films are very brittle and flexible. However, their microscopic scales present small patches of particular components from each starch. Immiscibility of the blends is gradually increased on adding the starch portions. Additional glycerol shows more strongly interfacial adhesion between starch and PHAs, and methanol produces specifically thin films. Melting transition temperatures of blended films are slightly higher than the biosynthesized PHAs as examined by DSC. Corn starch mixture causes highly brittle films than tapioca mixtures, which indicates poor adhesion between corn starch and the PHAs. This result is correspondent to their highly crystallinity from diffractogram. Microstructural evolution of the blended films is increased slightly crystallinity by the solution casting.