Rapid microwave assisted esterification method for the analysis of poly-3-hydroxybutyrate in Alcaligenes latus by gas chromatography

Microwave-Assisted Lignin Extraction-Utilizing Deep Eutectic Solvents to Their Full Potential

The current research intended to investigate the suitability of different choline-chloride-based deep eutectic solvents for their role in microwave lignin extraction. Lignin, a widely spread biopolymer in plants and woody structures, is a valuable replacement for fossil-fuel-based materials. While some promising applications have been trialled already, the extraction of this material from its matrix still causes problems. Here, we highlight an efficient and fast method to extract lignin from untreated larch bark with deep eutectic solvents in a standard domestic microwave. We developed a straightforward, green methodology, which can be used on various reaction scales, with materials available to many researchers. Lignin was extracted within only 30 min of microwave irradiation in yields of up to 96%. Compared to traditional deep eutectic extraction by conventional heating, the reaction time was cut by 87% and the energy costs were reduced by 93.5%. The hydrogen bond donors were exchanged and different types, namely acid-based, hydroxyl-based and amide-based donor systems, were evaluated for their suitability concerning microwave lignin extraction. This study presents a novel approach towards energy-efficient and green lignin valorisation, without the inherent need for costly equipment.

Direct determination of poly(3-hydroxybutyrate) accumulated in bacteria by thermally assisted hydrolysis and methylation-gas chromatography in the presence of organic alkali

There is considerable interest in the development of simple methods for quantifying production of the biodegradable polyester poly(3-hydroxybutyrate) [P(3HB)] by bacteria. Cells of Cupriavidus necator were grown on agar medium containing different concentrations of glucose (10–25 g/L) as a sole carbon source. Trace amounts (100±5 μg) of dried C. necator cells were directly subjected to thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) in the presence of tetramethylammonium hydroxide (TMAH). On the resulting chromatograms, a series of characteristic peaks, attributed to the THM products from poly(3-hydroxybutylate) accumulated in the bacterial cells, were clearly observed without any interfering component. Based on the peak intensities, the contents of P(3HB) in C. necator were determined precisely and rapidly without using any cumbersome sample pretreatment. Furthermore, the values of the P(3HB) contents coincided overall with those obtained by the conventional method involving solvent extraction followed by gravimetric determination.

Rapid and direct compositional analysis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in whole bacterial cells by thermally assisted hydrolysis and methylation-gas chromatography

Thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) in the presence of an organic alkali was applied to the direct analysis of copolymer composition for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] accumulated in whole bacterial cells. Cupriavidus necator was grown on a liquid medium with different molar ratios of valeric acid (V) to glucose (G) in order to control the compositions of P(3HB-co-3HV) produced in the cells. Trace amounts (0.03 mg) of dried Cupriavidus necator cells were directly subjected to THM-GC in the presence of tetramethylammonium hydroxide (TMAH) at 400°C. The obtained chromatograms clearly showed nine characteristic peaks, attributed to the THM products from 3HB and 3HV units in the polymer chains, without any appreciable interference by the bacterial matrix components. Based on these peak intensities, the copolymer compositions were determined rapidly without using any cumbersome sample pretreatment. Moreover, the compositions thus obtained were in good agreement with those obtained by the conventional technique.

Microwave-assisted extraction of lignin from triticale straw: optimization and microwave effects

Presently lignin is used as fuel but recent interests in biomaterials encourage the use of this polymer as a renewable feedstock in manufacturing. The present study was undertaken to explore the potential applicability of microwaves to isolate lignin from agricultural residues. A central composite design (CCD) was used to optimize the processing conditions for the microwave (MW)-assisted extraction of lignin from triticale straw. Maximal lignin yield (91%) was found when using 92% EtOH, 0.64 N H(2)SO(4), and 148 °C. The yield and chemical structure of MW-extracted lignin were compared to those of lignin extracted with conventional heating. Under similar conditions, MW irradiation led to higher lignin yields, lignins of lower sugar content, and lignins of smaller molecular weights. Except for these differences the lignins resulting from both types of heating exhibited comparable chemical structures. The present findings should provide a clean source of lignin for potential testing in manufacturing of biomaterials.

Microwave-assisted hydrolysis of nitroglycerin (NG) under mild alkaline conditions: new insight into the degradation pathway

Nitroglycerin (NG), a nitrate ester, is widely used in the pharmaceutical industry and as an explosive in dynamite and as propellant. Currently NG is considered as a key environmental contaminant due to the discharge of wastewater tainted with the chemical from the military and pharmaceutical industry. The present study describes hydrolytic degradation of NG (200 microM) at pH 9 using either conventional or microwave-assisted heating at 50 degrees C. We found that hydrolytic degradation of NG inside the microwave chamber was much higher than its degradation using conventional heating. Products distributions in both heating systems were closely related and included nitrite, nitrate, formic acid, and the novel intermediates 2-hydroxypropanedial (OCHCH(OH)HCO) and glycolic acid (CH2(OH)COOH). Two other intermediates glycolaldehyde (CH2(OH)CHO) and glyoxylic acid (CHOCOOH) were only detected in the microwave treated samples. The molar ratio of nitrite to nitrate in the presence and absence of microwave heating was 2.5 and 2.8, respectively. In both microwave assisted and conventional heating a nitrogen mass balance of 96% and 98% and a carbon mass balance of 58% and 78%, respectively, were obtained. The lower C mass recovery might be attributed to further unknown reactions, e.g., polymerization of the aldehydes CH2(OH)CHO, CHOCOOH and OCHCH(OH)HCO. A hydrolytic degradation pathway for NG was proposed involving denitration (loss of 2 NO2(-)) from the two primary carbons and the loss of one nitrate from the secondary carbon to produce 2-hydroxypropanedial.