The oil palm mesocarp contains an endogenous lipase which is strongly activated at low temperature. Lipase activity is thus very conveniently assayed by prior exposure of the fruits to low temperature. More than 100 oil palm samples from the germplasm collection of the Palm Oil Research Institute of Malaysia (now known as the Malaysian Palm Oil Board) were screened for non-esterified fatty acid activity using both the low-temperature activation assay and a radioactivity assay. The results showed good correlation between assay procedures. The different samples had a very wide range of lipase activity. Elaeis oleifera samples had significantly lower lipase activity compared with E. guineensis (var. tenera) samples. Even within E. guineensis (var. tenera), there was a wide range of activity. The results confirmed that lipase activity is genotype-dependent. Selection for lipase genotypes is thus possible and this will have obvious commercial value.
Mycelium-bound lipase (MBL), from a locally isolated Geotrichum candidum strain, was produced and characterized as a natural immobilized lipase. A time course study of its lipolytic activity in 1 L liquid broth revealed the maximum MBL activity at 4 h for mycelium cells harvested after 54 h. The yield and specific activity of MBL were 3.87 g/L dry weight and 508.33 U/g protein, respectively, while less than 0.2 U/mL lipase activity was detected in the culture supernatant. Prolonged incubation caused release of the bound lipase into the growth medium. The growth pattern of G. candidum, and production and properties of MBL were not affected by the scale. The stability of mycelia harboring lipase (MBL), harvested and lyophilized after 54 h, studied at 4 °C depicted a loss of 4.3% and 30% in MBL activity after 1 and 8 months, while the activity of free lipase was totally lost after 14 days of storage. The MBL from G. candidum displayed high substrate selectivity for unsaturated fatty acids containing a cis-9 double bond, even in crude form. This unique specificity of MBL could be a direct, simple and inexpensive way in the fats and oil industry for the selective hydrolysis or transesterification of cis-9 fatty acid residues in natural triacylglycerols.
In this work, the esterification of free fatty acids (FFA) in waste cooking oil catalysed by ferric sulphate was studied as a pre-treatment step for biodiesel production. The effects of reaction time, methanol to oil ratio, catalyst concentration and temperature on the conversion of FFA were investigated on a laboratory scale. The results showed that the conversion of FFA reached equilibrium after an hour, and was positively dependent on the methanol to oil molar ratio and temperature. An optimum catalyst concentration of 2 wt.% gave maximum FFA conversion of 59.2%. For catalyst loadings of 2 wt.% and below, this catalysed esterification was proposed to follow a pseudo-homogeneous pathway akin to mineral acid-catalysed esterification, driven by the H(+) ions produced through the hydrolysis of metal complex [Fe(H(2)O)(6)](3+) (aq).
Insulin resistance is characterized by hyperglycaemia, dyslipidaemia and oxidative stress prior to the development of type 2 diabetes mellitus. To date, a number of mechanisms have been proposed to link these syndromes together, but it remains unclear what the unifying condition that triggered these events in the progression of this metabolic disease. There have been a steady accumulation of data in numerous experimental studies showing the strong correlations between mitochondrial dysfunction, oxidative stress and insulin resistance. In addition, a growing number of studies suggest that the raised plasma free fatty acid level induced insulin resistance with the significant alteration of oxidative metabolism in various target tissues such as skeletal muscle, liver and adipose tissue. In this review, we herein propose the idea of long chain fatty acid-induced mitochondrial dysfunctions as one of the key events in the pathophysiological development of insulin resistance and type 2 diabetes. The accumulation of reactive oxygen species, lipotoxicity, inflammation-induced endoplasmic reticulum stress and alterations of mitochondrial gene subset expressions are the most detrimental that lead to the developments of aberrant intracellular insulin signalling activity in a number of peripheral tissues, thereby leading to insulin resistance and type 2 diabetes.
Only a few reports available about the assimilation of hydrophobic or oil-based feedstock as carbon sources by Lipomyces starkeyi. In this study, the ability of L. starkeyi to efficiently utilize free fatty acids (FFAs) and real biomass like palm acid oil (PAO) as well as crude palm kernel oil (CPKO) for growth and lipid production was investigated. PAO, CPKO, and FFAs were evaluated as sole carbon sources or in the mixed medium containing glucose. L. starkeyi was able to grow on the medium supplemented with PAO and FFAs, which contained long-chain length FAs and accumulated lipids up to 35% (w/w) of its dry cell weight. The highest lipid content and lipid concentration were achieved at 50% (w/w) and 10.1 g/L, respectively, when L. starkeyi was cultured in nitrogen-limited mineral medium (-NMM) supplemented with PAO emulsion. Hydrophobic substrate like PAO could be served as promising carbon source for L. starkeyi.
Isosteviol sodium (STVNa) is a beyerane diterpene synthesized via acid hydrolysis of stevioside, which can improve glucose and lipid metabolism in animals with diabetes. However, it remains unknown whether STVNa can exhibit a therapeutic effect on nonalcoholic fatty liver disease (NAFLD) and its underlying mechanism. We hypothesize that autophagic initiation may play a key role in mediating the development of NAFLD. Herein, we assessed the effects of STVNa on NAFLD and its underlying mechanisms. The results demonstrated that STVNa treatment effectively ameliorated NAFLD in rats fed high-fat diet (HFD). Moreover, STVNa decreased the expression of inflammation-related genes and maintained a balance of pro-inflammatory cytokines in NAFLD rats. STVNa also reduced lipid accumulation in free fatty acid (FFA)-exposed LO2 cells. In addition, STVNa attenuated hepatic oxidative stress and fibrosis in NAFLD rats. Furthermore, STVNa enhanced autophagy and activated Sirtuin 1/adenosine monophosphate-activated protein kinase (Sirt1/AMPK) pathway both in vivo and in vitro, thus attenuating intracellular lipid accumulation. In summary, STVNa could improve lipid metabolism in NAFLD by initiating autophagy via Sirt1/AMPK pathway. Therefore, STVNa may be an alternative therapeutic agent for treatment of NAFLD.
Rambutan seed is usually discarded during fruit processing. However, the seed contains a considerable amount of crude fat. Hence, the objective of this study was to investigate the fat properties and antinutrient content of the seed during fermentation of rambutan fruit. Results showed that the crude fat content of the seed reduced by 22% while its free fatty acid content increased by 4.3 folds after 10 days of fermentation. Arachidic acid was selectively reduced and was replaced by linoleic acid from the seventh day of fermentation onwards. Only 14.5% of triacylglycerol remained in the seed fat at the end of fermentation. The complete melting temperature, crystallization onset temperature and solid fat index at 37 °C of the fermented seed fat were higher than that of non-fermented seed fat. The saponin and tannin contents of the seed were reduced by 67% and 47%, respectively, after fermentation.