Search

Abstract: Reaction efficiencies of two organic alkalis, tetramethylammonium hydroxide (TMAH) and trimethylsulfonium hydroxide (TMSH), with lipids during thermally assisted hydrolysis and methylation (THM) were examined focusing on (1) the types of lipids and (2) degree of unsaturation of fatty acid moieties. Different types of lipids such as triglycerides, phospholipids, free fatty acids and cholesteryl esters containing saturated, monounsaturated or polyunsaturated fatty acid (PUFA) residues were subjected to THM-gas chromatography (GC) in the presence of TMAH or TMSH. The obtained results revealed that the THM reaction using TMAH allowed almost quantitative methylation of saturated and monounsaturated fatty acid components independently of the classes of lipids. However, strong alkalinity of TMAH brought about isomerization and/or degradation of PUFA components. In contrast, the use of TMSH was effective to highly sensitive detection of PUFA as well as saturated and monounsaturated fatty acid components contained in triglycerides, phospholipids (phosphatidylcholines) and free fatty acids. On the other hand, TMSH was proved to react hardly with any kind of fatty acid residues in cholesteryl esters due to their steric hindrance. [Copyright &y& Elsevier]

Thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) in the presence of trimethylsulfonium hydroxide (TMSH) was applied to the analysis of the lipid contents and their fatty acid compositions in individual zooplankters, especially focusing on polyunsaturated fatty acid (PUFA) components. On the resulting chromatograms, fatty acid components including PUFAs such as eicosapentaenoic acid (EPA; C20:5) and docosahexaenoic acid (DHA; C22:6) in single zooplankters were clearly observed as their methyl esters without doing any tedious and time-consuming pretreatment. By using this technique, the lipid contents and fatty acid compositions in a powdered plankter sample prepared by cryomilling homogenization were estimated on the basis of the observed peak intensities with relative standard deviations of less than 6%. The fatty acid compositions thus determined were in good agreement with those obtained by the conventional technique involving solvent extraction of the samples for every fatty acid component including PUFAs. The differences among individual zooplankter samples were then evaluated by THM-GC method. As a result, the chemical compositions of EPA and DHA showed relatively large inter-individual fluctuations even for the samples cultured under the same conditions. This suggests that lipid biosynthesis of the highly unsaturated fatty acid components and their consumption proceeded differently depending on the life history for each individual zooplankter. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Highlights • THM-GC was applied to monitor the change in copolymer composition of film samples during soil burial test. • 3 HHx moieties in the polymer chains were preferentially biodegraded owing to their low crystallinity. • Local variation in the degree of biodegradation using only 30 μg of P(3HB-co-3HHx) film sample. Abstract Soil burial biodegradation behavior of poly(3-hydroxybutyrate- co -3-hydroxyhexanoate) [P(3HB- co -3HHx)] was studied based on its copolymer composition determined by thermally assisted hydrolysis and methylation-gas chromatography (THM-GC). The change in copolymer composition of P(3HB- co -3HHx) film samples during soil burial degradation test was monitored in detail by THM-GC. As a result, the copolymer compositions of 3HB units gradually increased, while those of 3HHx units decreased with soil burial time, almost correlating with recovery weight. Based on these results, the biodegradation mechanism of P(3HB- co -3HHx) was elucidated with considering the influence of the crystallinity on the biodegradability. Furthermore, local differences in biodegradability of a given P(3HB- co -3HHx) film after soil burial test were also successfully evaluated from the copolymer compositions obtained by THM-GC. [ABSTRACT FROM AUTHOR]

Thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) in the presence of an organic alkali was validated for the compositional analysis of poly(3-hydroxybutyrate- co -3-hydroxyhexanoate) [P(3HB- co -3HHx)] accumulated in whole bacterial cells. Recombinant Cupriavidus necator Re2058/pCB113 was grown in a batch fermentation with different concentration of palm oil and fructose in order to control the molar fraction of 3HHx in P(3HB- co -3HHx) produced in the cells. Trace amounts (30 μg) of freeze-dried 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 3HHx 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 and lengthy sample pretreatment as in conventional GC method. Moreover, the compositions thus obtained were strongly correlated with those by NMR and conventional GC involving solvent extraction. [ABSTRACT FROM AUTHOR]

Abstract: In our previous paper, thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) measurements of poly(butylene succinate-co-butylene adipate) (PBSA) in the presence of tetramethylammonium hydroxide had revealed that the butylene adipate (BA) content in the PBSA films gradually decreased with soil burial degradation time. In order to clarify the cause of this change in copolymer composition, biodegradation behavior of PBSA with lowered crystallinity was evaluated by THM-GC. PBSA film samples with lower degree of crystallinity, prepared by heating and cooling quickly the original commercially available films, were subjected to a soil burial biodegradation test at 30°C for up to 4 weeks. The copolymer compositions between BA and butylene succinate (BS) units in various stages of the degraded film samples were estimated on the basis of chromatograms obtained by THM-GC with less than 5% of the relative standard deviations. As a result, the change in copolymer composition for the heated PBSA films during soil burial was relatively small compared to the original films, suggesting that biodegradation for the heated films proceeded with the comparable rate for both BA and BS-rich moieties due to lowered crystallinity. Based on these results, the reason for the change in copolymer composition observed for the original PBSA films was clarified as follows: (1) the BA-rich moieties in the copolymer chains could show relatively lower crystallinity than the BS-rich moieties and (2) the BA-rich moieties were preferentially biodegraded during soil burial test, leading to the decrease in the BA content as the biodegradation proceeded. [Copyright &y& Elsevier]

Biodegradability of poly(butylene succinate-co-butylene adipate) (PBSA) was studied based on its copolymer composition determined by thermally assisted hydrolysis and methylation-gas chromatography (THM-GC) using trace amounts (20 µg) of the film samples. The copolymer compositions of butylene adipate (BA) units gradually decreased with soil burial degradation time, reflecting preferential biodegradation of BA moieties during soil burial due to their lower crystallinity. Furthermore, local differences in biodegradability of a given PBSA film after soil burial were also successfully evaluated. [ABSTRACT FROM PUBLISHER]