Reaction Kinetics of Transesterification Between Palm Oil and Methanol under Subcritical Conditions

The objective of this work was to evaluate transesterification kinetics for biodiesel production from palm oil under subcritical conditions. Experimental investigation was carried out with palm oil and methanol at molar ratio of 46:1, temperatures between 150-200 °C and pressure around 140-190 atm in a 400 ml batch  reactor.  The biodiesel products were analyzed by gas chromatography – mass spectrometry. Area percentage method was used to estimate the methyl esters in the product. Zero- and first-order kinetic models were developed. Apparent activation energy was estimated to be in the range of 91-105 kJ/mol. The reaction rate equation was best approximated by the first order kinetic model with pre-exponential factor of 1.57 x 109.Key words: Biodiesel; Critical fluids; Kinetic equations; Methyl esters; Palm oil; Renewable energ

Isoprene-Degrading Bacteria from Soils Associated with Tropical Economic Crops and Framework Forest Trees

Isoprene, a volatile hydrocarbon emitted largely by plants, plays an important role in regulating the climate in diverse ways, such as reacting with free radicals in the atmosphere to produce greenhouse gases and pollutants. Isoprene is both deposited and formed in soil, where it can be consumed by some soil microbes, although much remains to be understood about isoprene consumption in tropical soils. In this study, isoprene-degrading bacteria from soils associated with tropical plants were investigated by cultivation and cultivation-independent approaches. Soil samples were taken from beneath selected framework forest trees and economic crops at different seasons, and isoprene degradation in soil microcosms was measured after 96 h of incubation. Isoprene losses were 4–31% and 15–52% in soils subjected to a lower (7.2 × 105 ppbv) and a higher (7.2 × 106 ppbv) concentration of isoprene, respectively. Sequencing of 16S rRNA genes revealed that bacterial communities in soil varied significantly across plant categories (framework trees versus economic crops) and the presence of isoprene, but not with isoprene concentration or season. Eight isoprene-degrading bacterial strains were isolated from the soils and, among these, four belong to the genera Ochrobactrum, Friedmanniella, Isoptericola and Cellulosimicrobium, which have not been previously shown to degrade isoprene

Genome characterisation of an isoprene-degrading Alcaligenes sp. isolated from a tropical restored forest

Isoprene is a climate-active biogenic volatile organic compound (BVOC), emitted into the atmosphere in abundance, mainly from terrestrial plants. Soil is an important sink for isoprene due to its consumption by microbes. In this study, we report the ability of a soil bacterium to degrade isoprene. Strain 13f was isolated from soil beneath wild Himalayan cherry trees in a tropical restored forest. Based on phylogenomic analysis and an Average Nucleotide Identity score of >95%, it most probably belongs to the species Alcaligenes faecalis. Isoprene degradation by Alcaligenes sp. strain 13f was measured by using gas chromatography. When isoprene was supplied as the sole carbon and energy source at the concentration of 7.2 × 105 ppbv and 7.2 × 106 ppbv, 32.6% and 19.6% of isoprene was consumed after 18 days, respectively. Genome analysis of Alcaligenes sp. strain 13f revealed that the genes that are typically found as part of the isoprene monooxygenase gene cluster in other isoprene-degrading bacteria were absent. This discovery suggests that there may be alternative pathways for isoprene metabolism

Development of HPLC Method for Catechins and Related Compounds Determination and Standardization in Miang (Traditional Lanna Fermented Tea Leaf in Northern Thailand)

High performance liquid chromatography (HPLC) for catechins and related compounds in Miang (traditional Lanna fermented tea leaf) was developed to overcome the matrices during the fermentation process. We investigated a variety of columns and elution conditions to determine seven catechins, namely (+)-catechin, (−)-gallocatechin, (−)-epigallocatechin, (−)-epicatechin, (−)-epigallocatechin gallate, (−)-gallocatechin gallate, (−)-epicatechin gallate, as well as gallic acid and caffeine, resulting in the development of reproducible systems for analyses that overcome sample matrices. Among the three reversed-phase columns, column C (deactivated, with extra dense bonding, double endcapped monomeric C18, high-purity silica at 3.0 mm × 250 mm and a 5 µm particle size) significantly improved the separation between Miang catechins in the presence of acid in the mobile phase within a shorter analysis time. The validation method showed effective linearity, precision, accuracy, and limits of detection and quantitation. The validated system was adequate for the qualitative and quantitative measurement of seven active catechins, including gallic acid and caffeine in Miang, during the fermentation process and standardization of Miang extracts. The latter contain catechins and related compounds that are further developed into natural active pharmaceutical ingredients (natural APIs) for cosmeceutical and nutraceutical products

Effects of chitosan and salicylic acid on Stemona alkaloid production in hydroponic culture of Stemona curtisii Hook. f.

The objective of this study was to investigate the effects of the elicitors, salicylic acid (SA) and chitosan, on the improvement of Stemona alkaloid production in hydroponic cultures of S. curtisii. In vitro plantlets were used as plant materials. The elicitors were added into the culture medium and samples of the roots and medium were collected on week 2 and 4 after the elicitor addition and then analyzed for Stemona alkaloid production by high performance liquid chromatography (HPLC). This study revealed that both SA and chitosan increased production of three Stemona alkaloids and that chitosan is better than SA for the enhancement of the production of these alkaloids. The elicitation by 20 mg L-1 of chitosan for 4 weeks induced highest amount of oxyprotostemonine (274.31 μg g-1 DW) stemocurtisine (35.46 μg g-1 DW) and stemocurtisinol (99.48 μg g-1 DW), which were 1.9, 2.0 and 1.5 fold higher than that of the control, respectively

Response of Stemona alkaloid production in Stemona sp. to chitosan and yeast extract elicitors

The experiments were purposed to investigate the effect of chitosan and yeast extract on Stemona alkaloid production in Stemona sp. culture. Both elicitors enhanced Stemona alkaloid production over the control. Treatment with chitosan at a concentration of 25 mg/L for 1 week resulted in the highest production of Stemona alkaloids. It was found that 1\u27, 2\u27-didehydrostemofoline and stemofoline production was 2.65 fold and 2.95 fold higher than the control, respectively

Chemical diversity and anti-acne inducing bacterial potentials of essential oils from selected Elsholtzia species

Essential oils from the aerial parts of four Elsholtzia species; Elsholtzia stachyodes, Elsholtzia communis, Elsholtzia griffithii and Elsholtzia beddomei were obtained by steam distillation and their chemical components were analysed by gas chromatography-mass spectrometry (GC-MS). Principle Component Analysis was used to identify the chemical variations in the essential oils from these plants, which could be categorised into two groups according to their main chemical components which are acylfuran derivatives and oxygenated monoterpenes. Additionally, the anti-acne inducing bacterial activity against Staphylococcus aureus and Staphylococcus epidermidis were evaluated. The oil from E. stachyodes was the most efficacious against the growth of S. aureus and S. epidermidis having MIC values of 0.78 and 1.56 μL/mL, respectively, and exhibited five times more effective than erythromycin (standard antibiotic)

Response of Stemona alkaloid Production in Stemona sp. to Chitosan and Yeast Extract Elicitors

Abstract: The experiments were purposed to investigate the effect of chitosan and yeast extract on Stemona alkaloid production in Stemona sp. culture. Both elicitors enhanced Stemona alkaloid production over the control. Treatment with chitosan at a concentration of 25 mg/L for 1 week resulted in the highest production of Stemona alkaloids. It was found that 1', 2'-didehydrostemofoline and stemofoline production was 2.65 fold and 2.95 fold higher than the control, respectively

Utilization of electrocoagulation for the isolation of alkaloids from the aerial parts of Stemona aphylla and their mosquitocidal activities against Aedes aegypti

The electrocoagulation (EC) technique is an alternative method of isolating natural products with the advantage of minimizing the amounts of organic solvents required for this process, which are often harmful to the environment. In this research, the EC and the conventional solvent extraction methods were used in the isolation of Stemona alkaloids from the aerial parts of Stemona aphylla. A comparison was made between the amounts of the isolated alkaloids and the solvents used. The isolated alkaloids were evaluated for their larvicidal, ovicidal and oviposition-deterrent activities against the dengue vector, Aedes aegypti. The morphology and histopatology of the alkaloid treated larvae were also investigated. Two Stemona alkaloids, (2′S)-hydroxystemofoline and stemofoline, were isolated from both the EC and the conventional method. The amounts of (2′S)-hydroxystemofoline from the EC method was about the same as that obtained from the conventional method. However, the amounts of stemofoline obtained from the EC method were about two times larger than those obtained from the conventional method. Importantly, the EC method required six times less total organic solvents. The larvicidal activity assays of (2′S)-hydroxystemofoline and stemofoline showed that these were highly effective against Aedes aegypti larvae with LC50 values of 3.91 μg/ml and 4.35 μg/ml, respectively. Whereas, the crude EC extract (LC50 = 11.86 μg/ml) showed greater larvicidal activity than the crude extract obtained from the conventional extraction method (LC50 = 53.40 μg/ml). The morphological observations of the (2′S)-hydroxystemofoline and the stemofoline treated larvae revealed that the anal gills were the sites of aberrations. A histopathological study showed that larvae treated with these alkaloids had cytopathological alterations to the epithelial cells of the midgut. At a concentration 40 μg/ml (2′S)-hydroxystemofoline showed 100% ovicidal activity on 24 h old eggs while stemofoline showed 97.2%. Furthermore, the oviposition-deterrent effects of (2′S)-hydroxystemofoline and stemofoline, at a concentration of 80 μg/ml were 99.5% and 97.2%, respectively