A Simple Method for the Detection of Long-Chain Fatty Acids in an Anaerobic Digestate Using a Quartz Crystal Sensor

Abstract

Abstract:In anaerobic digestion (AD), long-chain fatty acids (LCFAs) produced by hydrolysis of lipids, exhibit toxicity against microorganisms when their concentration exceeds several millimolar. An absorption detection system using a quartz crystal microbalance (QCM) was developed to monitor the LCFA concentration during an anaerobic digester's operation treating oily organic waste. The dissociation of the LCFAs considerably improved the sensor response and, moreover, enabled it to specifically detect LCFA from the mixture of LCFA and triglyceride. Under alkaline conditions, the frequency-shift rates of the QCM sensor linearly increased in accordance with palmitic acid concentration in the range of 0-100 mg/L. Frequency changes caused by anaerobic digestate samples were successfully measured after removing suspended solids and adjusting the pH to 10.7. Finally, the QCM measurements for digestate samples demonstrated that frequency-shift rates are highly correlated with LCFA concentrations, which confirmed that the newly developed QCM sensor is helpful for LCFA monitoring in terms of rapidness and usability.

Taxonomic and Functional Variations Induced by an Overloading Event in Anaerobic Codigestion of Municipal Wastewater Sludge with Fats, Oils, and Grease

“…Analytical techniques for LCFA detection involve complex sample processing followed by gas chromatography, which requires expensive instrumentation, time, and additional personnel training. Kobayashi et al 51 demonstrated the use of a quartz crystal sensor to monitor LCFA concentrations in AD processes. Further development of more easily employed methods of LCFA detection, such as a quartz crystal sensor, would likely be needed for feasible and widely recommended monitoring of palmitic acid.…”

From unavoidable food waste to advanced biomaterials: microfibrilated lignocellulose production by microwave-assisted hydrothermal treatment of cassava peel and almond hull

“…Interestingly, the sugar analysis for the AH hydrolysate with heptane pretreatment did not identify the presence of rhamnose or galacturonic acid at a temperature of 120°C. The extracted compounds from the lipids present in the biomass may be capable of altering the pKa of the reaction medium (e.g., from short/long fatty acid and rhamnolipids) and then, possibly the water contained in the medium may affect the polymerization of the sugar acids and rhamnose during Soxhlet extraction (Kobayashi et al 2017;Soltani Dashtbozorg et al 2019). Scissoring of amorphous cellulose and hemicellulose compounds depends on the operating microwave temperature (Xia et al 2016;De Melo et al 2017).…”

Determination of long-chain fatty acids in anaerobic digester supernatant and olive mill wastewater exploiting an in-syringe dispersive liquid-liquid microextraction and derivatization-free GC-MS method

“…The pKa of LCFA in water is estimated to be around 4.8 [37], but in 50% (v/v) ethanol-water mixtures (equivalent to a 0.24 mol fraction) the pKa rises to 7.0 [38]. Other authors state that pKa of C14, C16, and C18 fatty acids in water are in the range of 8.1-10.5 [9,39]. As the dissociation can occur at pH > pKa (allowing LCFA to dissolve easily in water) and the usual pH of wastewater is close to neutral, LCFA are insoluble in this medium and float on the surface.…”

“…In the anaerobic digestion process, long-chain fatty acids (LCFA) such as myristic, palmitic, stearic, oleic, and linoleic acids are produced by lipid hydrolysis from the FOG found in wastewater [4]. LCFA can be present or anaerobically produced from dairy wastewater [5], oil wastewater [6], fish waste [7], slaughterhouse wastewater [8], and vegetable waste from restaurants [9] or food processing industries such as olive mill wastewater (OMW), the liquid by-product obtained from olive oil production [10].…”