Synthesis of 2‐monoglycerides by alcoholysis of palm oil and tuna oil using immobilized lipases

Commercial immobilized lipases were used for the synthesis of 2‐monoglycerides (2‐MG) by alcoholysis of palm and tuna oils with ethanol in organic solvents. Several parameters were studied, i.e., the type of immobilized lipases, water activity, type of solvents and temperatures. The optimum conditions for alcoholysis of tuna oil were at a water activity of 0.43 and a temperature of 60 °C in methyl‐tert‐butyl ether for ～12 h. Although immobilized lipase preparations from Pseudomonas sp. and Candida antarctica fraction B are not 1, 3‐regiospecific enzymes, they were considered to be more suitable for the production of 2‐MG by the alcoholysis of tuna oil than the 1, 3‐regiospecific lipases (Lipozyme RM IM from Rhizomucor miehei and lipase D from Rhizopus delemar). With Pseudomonas sp. lipase a yield of up to 81% 2‐MG containing 80% PUFA (poly‐unsaturated fatty acids) from tuna oil was achieved. The optimum conditions for alcoholysis of palm oil were similar as these of tuna oil alcoholysis. However, lipase D immobilized on Accurel EP100 was used as catalyst at 40 °C with shorter reaction times (<12 h). This lead to a yield of ～60% 2‐MG containing 55.0‐55.7% oleic acid and 18.7‐21.0% linoleic acid.     

Solubilization of Hydrophobic Catalysts Using Nanoparticle Hosts

A modular strategy for the solubilization and protection of hydrophobic transition metal catalysts using the hydrophobic pockets of water soluble gold nanoparticles is reported. Besides preserving original catalyst activity, this encapsulation strategy provides a protective environment for the hydrophobic catalyst and brings reusability. This system provides a versatile platform for the encapsulation of different hydrophobic transition metal catalysts, allowing a wide range of catalysis in water while uniting the advantages of homogeneous and heterogeneous catalysis in the same system.     

Simultaneous thermophilic hydrogen production and phenol removal from palm oil mill effluent by Thermoanaerobacterium-rich sludge

Thermoanaerobacterium-rich sludge was used for hydrogen production and phenol removal from palm oil mill effluent (POME) in the presence of phenol concentration of 100–1000 mg/L. Thermoanaerobacterium-rich sludge yielded the most hydrogen of 4.2 L H₂/L-POME with 65% phenol removal efficiency at 400 mg/L phenol. Butyric acid and acetic acid were the main metabolites. The effects of oil palm ash, NH₄NO₃ and iron concentration (Fe²⁺) on hydrogen production and phenol removal efficiency from POME by Thermoanaerobacterium-rich sludge was investigated using response surface methodology (RSM). The RSM results indicated that the presence of 0.2 g Fe²⁺/L, 0.3 g/L NH₄NO₃ and 20 g/L oil palm ash in POME could improved phenol removal efficiency, with predicted hydrogen production and phenol removal efficiency of 3.45 L H₂/L-POME and 93%, respectively. In a confirmation experiment under optimized conditions highly reproducible results were obtained, with hydrogen production and phenol removal efficiency of 3.43 ± 0.12 L H₂/L-POME and 92 ± 1.5%, respectively. Simultaneous hydrogen production and phenol removal efficiency in continuous stirred tank reactor at hydraulic retention time (HRT) of 1 and 2 days were 4.0 L H₂/L-POME with 85% and 4.2 L H₂/L-POME with 92%, respectively. Phenol degrading Thermoanaerobacterium-rich sludge comprised of Thermoanaerobacterium thermosaccharolyticum, Thermoanaerobacterium aciditolerans, Desulfotomaculum sp., Bacillus coagulans and Clostridium uzonii. Phenol degrading Thermoanaerobacterium-rich sludge has great potential to harvest hydrogen from phenol-containing wastewater.     

Changes in microbiological, biochemical and physico-chemical properties of Nham inoculated with different inoculum levels of Lactobacillus curvatus

The effect of inoculum level of Lactobacillus curvatus on Nham fermentation was studied. Nham inoculated with L. curvatus at 10⁴ (LC104) and 10⁶ cfu/g (LC106) exhibited a higher rate of fermentation than naturally fermented Nham (control) as indicated by greater rate of pH drop, lactic acid production, and changes in protein compositions. Based on the pH, the fermentation was completed within 72, 48 and 36 h for control, LC104, and LC106, respectively. Higher extent of proteolysis and lipolysis were observed during fermentation of Nham inoculated with starter bacteria (P<0.05). Due to higher acid production rate and extent, texture development of inoculated Nham was more rapid. Inoculated Nham exhibited higher TPA hardness and adhesiveness but lower fracturability than naturally fermented Nham (P<0.05). In terms of acceptability, control and LC104 had higher ratings on the overall liking than LC106 (P<0.05). However, LC104 was better accepted than control in terms of flavour, sourness, saltiness, and texture. Unusual smell was detected only in Nham inoculated at 10⁶ cfu/g. Based on physico-chemical properties and consumer acceptability, L. curvatus is a potential starter for Nham fermentation. However, inoculation of L. curvatus at high level may cause off-flavour in the product.     

Lipase‐catalyzed acidolysis and phospholipase D‐catalyzed transphosphatidylation of phosphocholine

Two approaches on enzymatic phospholipid modification were studied: (1) transphosphatidylation of the 1,2‐dilauroyl‐sn‐glycero‐3‐phosphocholine (DLPC) and ethanolamine in biphasic and anhydrous organic solvent systems by phospholipase D (PLD) and (2) incorporation of oleic acid into the sn1‐position of DLPC in organic solvents with different immobilized lipases at controlled water activity. First, DLPC was chemically synthesized from glycerophosphocholine and lauric acid. Next, PLD‐catalyzed head group exchange of DLPC with ethanolamine was studied using an enzyme from Streptomyces antibioticus expressed recombinantly in E. coli. A comparison of the free PLD with the biocatalyst activated by a salt‐activation technique using KCl showed that the salt‐activated enzyme (PLD‐KCl) was 10–12 folds more active based on the amount of protein used. Thus, DLPC was quantitatively converted to 1,2‐dilauroyl‐sn‐glycero‐3‐phosphoethanolamine in an anhydrous solvent system within 12 h at 60 °C. For the acidolysis of DLPC with oleic acid, among the four lipases studied (CAL‐B, Lipozyme TL IM, Lipozyme RM IM and lipase D immobilized on Accurel EP‐100), Lipozyme TL IM showed the highest activity and incorporation of oleic acid. A quantitative incorporation was achieved at 40 °C using a 8‐fold molar excess of oleic acid in n‐hexane at a water activity of 0.11.     

Influence of minced pork and rind ratios on physico-chemical and sensory quality of Nham - a Thai fermented pork sausage

The effects of incorporating varying levels of minced pork and rind on physico-chemical and sensory quality of Nham were studied. An increase in cooked pork rind resulted in higher moisture, lipid, and initial pH values of Nham (P<0.05). However, no significant effects were observed on fermentation characteristics of Nham (P>0.05). At the end of fermentation, Nham with a higher meat component exhibited higher texture profile analysis force, hardness, and cohesiveness (P<0.05). The results suggested the importance of meat on the restructuring effect, which contributes to the texture formation of Nham. Incorporation of a higher amount of cooked pork rind improved water-binding properties, leading to decreased weight loss and released water. Based on the results of sensory evaluation, up to 43% pork rind can be used in the formulation with no adverse effect on texture and overall liking of Nham. However, the ratio of 5:5 was the most appropriate for minimising the cost of production.     

Probiotic lactic acid bacteria from Kung‐Som: isolation,screening, inhibition of pathogenic bacteria

Lactic acid bacteria (LAB) were isolated from Kung‐Som at various fermentation periods. Only ten strains, named D2SM22, D6SM3, D6SM24, D6SM26, D8SM21, D10SM5, D10SM11, D10SM16, D10SM20 and D16SM26 showed a survival rate of more than 50% under the simulated gastric juice. After being subjected to simulated gastric juice, four strains (D6SM3, D8SM21, D10SM16 and D10SM20) showed a survival rate of more than 50% in simulated small intestinal juices. Growth of strain D6SM3, D8SM21 and D10SM16 under micro‐aerobic and anaerobic conditions was not different. Tested pathogenic strains (Escherichia coli, Staphylococcus aureus, Bacillus cereus, Vibrio parahaemolyticus and Salmonella sp.) were inhibited by probiotic LAB. However, none of strains could produce bacteriocins. All strains were identified as Lactobacillus plantarum. No differences in pH, acidity, LAB count and liking scores between Kung‐Som produced with starter culture and conventional method were observed (P > 0.01).     

Microbial community analysis of thermophilic mixed culture sludge for biohydrogen production from palm oil mill effluent

The microbial community structure of thermophilic mixed culture sludge used for biohydrogen production from palm oil mill effluent was analyzed by fluorescence in situ hybridization (FISH) and 16S rRNA gene clone library techniques. The hydrogen-producing bacteria were isolated and their ability to produce hydrogen was confirmed. The microbial community was dominated by Thermoanaerobacterium species (∼66%). The remaining microorganisms belonged to Clostridium and Desulfotomaculum spp. (∼28% and ∼6%, respectively). Three hydrogen-producing strains, namely HPB-1, HPB-2, and HPB-3, were isolated. 16S rRNA gene sequence analysis of HPB-1 and HPB-2 revealed a high similarity to Thermoanaerobacterium thermosaccharolyticum (98.6% and 99.0%, respectively). The Thermoanaerobacterium HPB-2 strain was a promising candidate for thermophilic fermentative hydrogen production with a hydrogen yield of 2.53 mol H₂ mol⁻¹hexose from organic waste and wastewater containing a mixture of hexose and pentose sugars. Thermoanaerobacterium species play a major role in thermophilic hydrogen production as confirmed both by molecular and cultivation-based analyses.