No abstract

Background Sugars and triglycerides are common carbon sources for microorganisms. Nonetheless, a systematic comparative interpretation of metabolic changes upon vegetable oil or glucose as sole carbon source is still lacking. Selected fungi that can grow in acidic mineral salt media (MSM) with vegetable oil had been identified recently. Hence, this study aimed to investigate the overall metabolite changes of an omnipotent fungus and to reveal changes at central carbon metabolism corresponding to both carbon sources. Results Targeted and non-targeted metabolomics for both polar and semi-polar metabolites of Phialemonium curvatum AWO2 (DSM 23903) cultivated in MSM with palm oil (MSM-P) or glucose (MSM-G) as carbon sources were obtained. Targeted metabolomics on central carbon metabolism of tricarboxylic acid (TCA) cycle and glyoxylate cycle were analysed using LC–MS/MS-TripleQ and GC–MS, while untargeted metabolite profiling was performed using LC–MS/MS-QTOF followed by multivariate analysis. Targeted metabolomics analysis showed that glyoxylate pathway and TCA cycle were recruited at central carbon metabolism for triglyceride and glucose catabolism, respectively. Significant differences in organic acids concentration of about 4- to 8-fold were observed for citric acid, succinic acid, malic acid, and oxaloacetic acid. Correlation of organic acids concentration and key enzymes involved in the central carbon metabolism was further determined by enzymatic assays. On the other hand, the untargeted profiling revealed seven metabolites undergoing significant changes between MSM-P and MSM-G cultures. Conclusions Overall, this study has provided insights on the understanding on the effect of triglycerides and sugar as carbon source in fungi global metabolic pathway, which might become important for future optimization of carbon flux engineering in fungi to improve organic acids production when vegetable oil is applied as the sole carbon source.

Palm oil is produced from oil palm fruits, Elaeis guineensis, and the extracted oil is known as crude palm oil (CPO) (Sundram et al., 2003).CPO is typically delivered to a refinery for a subsequent processing to produce edible palm oil. CPO contains predominantly neutral oil, also known as triacylglycerol (TAG), along with other minor constituents including free fatty acid (FFA), diacylglycerol (DAG), monoacylglycerol (MAG), moisture, solid impurities, phospholipids, antioxidants (such as carotenes, tocopherols, sterols), lipid oxidation products, metal contents, and chlorides Maclellan, 1983;Mancini et al., 2015). These minor constituents are impacting the overall quality of the CPO produced. In the palm oil industry, CPO quality specifications set by the Palm Oil Refiners Association of Malaysia (PORAM) are commonly used as a standard quality requirement for the trading of CPO between millers and refiners, illustrated in Table 1 (PORAM, 2000). According to the standard, the FFA indicates the hydrolytic stability of the oil and the deterioration of bleachability index (DOBI) implies the acceptance level in the refining process. Lastly, the moisture and impurities (M&I) determine the purity of the CPO produced (Ariffin, 2001;Chong, 2012).Generally, the CPO is susceptible to lipid oxidation, causing oil instability and reduces shelf life (Frega et al., 1999). During production,

The processing of oil palm fresh fruit bunches (FFB), together with loose fruits, in the current mill operation contributes to oil loss and high free fatty acids (FFA), affecting crude palm oil quality. Fruit detachment induced by ethephon and ethylene may mitigate the current processing issues. This study shows that a 0.50% (v/v) ethephon application by the evaporation method induced the highest fruit detachment of 30.8 ± 1.1% after 24 h at room temperature, with the FFA content in the extracted crude palm oil at 0.34 ± 0.09%. Ethephon application was effective on bunches between 14 and 28 kg, and fruit detachment was higher in ripe and underripe bunches at 24.1 ± 0.9% and 23.2 ± 0.1%, respectively. A significant fruit detachment of 47.2 ± 2.4% was achieved when the bunches were also stripped mechanically, but the FFA content increased almost 4-fold, from 1.0 ± 0.2% to 3.8 ± 1.2%. The application of ethylene gas at 750 ppm yielded 29.4 ± 1.9% fruit detachment. The findings present the possibility of using ethylene as an indirect method for minimizing oil loss without increasing the FFA content in future crude palm oil production systems.

Background: The level of free fatty acids (FFAs) is an important oil quality index that is consistently measured at mills and refineries to ensure that palm oil is within specification limits. FFAs can accumulate at any point throughout the process, for example, during fresh fruit bunch (FFB) harvesting or during the mill process before sterilisation. Another key contributor to FFA build-up is loose fruit (LF), which is collected following FFB harvesting and is commonly processed together with FFB into crude palm oil (CPO) at the mill. The aim of this study was to identify pivotal points of FFA formation during the process of crude palm oil production. Results: The present study shows that the highest FFA accumulation occurred during the conveying process at the mill before sterilisation due to significant fruit damage. The rapid formation of FFA occurred during the first 15 min of oil palm fruit bruising. A minimum temperature of 60 °C for one hour was needed to deactivate the lipase activity, which is responsible for FFA formation. Blending high-FFA CPO with standard CPO affected indices of palm oil quality, such as the deteriorated peroxide value (PV) and anisidine value (AV), and particularly worsened the bleachability index (DOBI). Conclusions: This study suggests that the conveyor system in the mill could be the prime area to focus on in terms of FFA reduction, along with minimising bruising events. In addition, loose fruits (LF) with high FFA content should be processed separately from FFB, and high-FFA CPO derived from LF should not be mixed with standard CPO.