RESUMEN
Polyhydroxyalkanoates (PHAs) have attracted attention as an environmentally degradable bioplastic which potentially replaces synthetic polymers used in a wide range of industries. One of most promising microorganisms for the production of PHAs is Pseudomonas putida. In this study, we purpose to develop sustainable processes to convert abundant palm oil available in local market to high value PHAs and optimize PHAs production by Pseudomonas putida TISTR 1522 from saponified palm oil. We found that the highest yield of PHAs production (0.95 g/L, 40.15%) was obtained in culture medium supplemented with 1% (w/v) fatty acid salt by P. putida TISTR 1522 after 24-h cultivation. The intracellular PHAs were located in granules inside the cells, which fluoresced bright yellow by staining with Nile red. The physical appearance of intracellular PHAs investigated by transmission electron microscope (TEM) revealed that PHAs accumulate in granules, about 3-10 granules per cell. These granules are white and roundish-shaped with 0.3-0.5-µm diameter. The 1H NMR spectrum represented the typical characters of medium-chain length-PHAs. This variation of all parameters was successfully demonstrated a good intracellular PHAs accumulation in P. putida TISTR 1522 by fatty acid salt utilization.
Asunto(s)
Técnicas de Cultivo Celular por Lotes , Aceite de Palma/química , Polihidroxialcanoatos/biosíntesis , Pseudomonas putida/crecimiento & desarrollo , Aceite de Palma/metabolismoRESUMEN
Long-chain alkyl glucosides, such as octyl and decyl ß-d-glucopyranosides (OG and DG, respectively), are regarded as a new generation of biodegradable, non-ionic surfactants. Previously, the mutants of Dalbergia cochinchinensis Pierre dalcochinase showed potential in the synthesis of oligosaccharides and alkyl glucosides. In this study, the N189F dalcochinase mutant gave the highest yields of OG and DG synthesis under reverse hydrolysis conditions. The optimized yield of OG (57.5â¯mol%) was obtained in the reactions containing 0.25â¯M glucose and 0.3 units of the N189â¯F mutant in buffer-saturated octanol at 30⯰C. The identity of OG and DG products was confirmed by high resolution mass spectrometry (HRMS) and NMR. Consistent with its capability for synthesis, the reactivation kinetics and ITC analysis revealed that the aglycone binding pocket of the N189F mutant was more favorable for long-chain alkyl alcohols than the wild-type dalcochinase, while their glycone binding pockets showed similar affinity for the glucosyl moiety. STD NMR revealed higher interactions at the aglycone sites than the glycone sites. Our results demonstrated a promising potential of the N189F dalcochinase mutant in the future commercial production of long-chain alkyl glucosides via reverse hydrolysis reactions.
Asunto(s)
Glucósidos/metabolismo , beta-Glucosidasa/metabolismo , Alcoholes/química , Alcoholes/metabolismo , Catálisis , Dalbergia/enzimología , Glucosa/metabolismo , Glucósidos/química , Cinética , Modelos Moleculares , Mutación , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , beta-Glucosidasa/química , beta-Glucosidasa/genéticaRESUMEN
OBJECTIVE: To synthesize octyl ß-D-glucopyranoside (OG) and decyl ß-D-glucopyranoside (DG) in three non-aqueous reaction systems, namely organic solvents, ionic liquids and co-solvent mixtures, via reverse hydrolysis reactions catalyzed by the N189F dalcochinase mutant. RESULTS: The highest yield of OG (67 mol%) was obtained in the reaction containing 0.5 M glucose, 3 unit ml-1 enzyme in 20% (v/v) octanol and 70% (v/v) [BMIm][PF6] at 30 °C. On the other hand, the highest yield of DG (64 mol%) was obtained in the reaction containing 0.5 M glucose, 3 unit ml-1 enzyme in 20% (v/v) decanol, 20% (v/v) acetone and 50% (v/v) [BMIm][PF6] at 30 °C. The identities of OG and DG products were confirmed by HRMS and NMR. CONCLUSION: This is the first report of enzymatic synthesis of OG and DG via reverse hydrolysis reactions in ionic liquids and co-solvent mixtures. The N189F dalcochinase mutant and the non-aqueous reaction systems described here show great potential for future commercial production of long-chain alkyl glucosides.
Asunto(s)
Galactósidos/química , Solventes/química , beta-Glucosidasa/metabolismo , Hidrólisis , Líquidos Iónicos/química , Ingeniería de ProteínasRESUMEN
Dalcochinase from Dalbergia cochinchinensis Pierre and linamarase from Manihot esculenta Crantz are ß-glucosidases which share 47% sequence identity, but show distinct substrate specificities in hydrolysis and transglucosylation. Previously, three amino acid residues of dalcochinase, namely I185, N189 and V255, were identified as being important for determining substrate specificity. In this study, kinetic analysis of the ensuing double and triple mutants of dalcochinase showed that only those containing the 185A mutation could appreciably hydrolyze linamarin as well as transfer glucose to 2-methyl-2-propanol. So, the space provided by the I185A mutation appeared to be a prerequisite for accommodation of the aglycone moiety containing three substituents at the carbinol carbon. However, quantitative analysis of the energy parameters revealed mostly antagonistic interactions between these mutations. In addition, the N189F mutant showed a potential for use in enzymatic synthesis of alkyl glucosides via transglucosylation and reverse hydrolysis reactions. Thus, substitution of only 2-3 key residues in the aglycone binding pocket of dalcochinase could convert its specificities to that of linamarase, as well as to be suitable for any chosen hydrolytic or synthetic applications.