Content uploaded by Susan B. Watson
Author content
All content in this area was uploaded by Susan B. Watson on Dec 27, 2020
Content may be subject to copyright.
Algal taste and odor
... Fishy odor problems often occur in cold water, even under ice-covered water with low nutrient concentrations. The occurrence of fishy odor has been associated with algal metabolites, mainly polyunsaturated aldehydes (PUAs), such as 2,4-heptadienal, 2,4decadienal, and 2,4,7-dectridienal (Pohnert 2002;Watson 2010;Wendel and Jüttner 1996). Some saturated aldehydes, e.g., hexanal, heptanal, and benzaldehyde, were also assumed to contribute to fishy odor Venkateshwarlu et al. 2004). ...
An investigation of odor distribution characteristics in source and drinking water of 98 drinking water treatment plants in 31 cities across China was carried out based on a high-throughput quantification method for 95 odorants using gas chromatography-triple quadrupole tandem mass spectrometry (GC–MS/MS) and Flavor Profile Analysis. The national investigation showed that about 90% of source water samples exhibited odor problems with earthy/musty (31.8%) and swampy/septic (45.4%) odors as the dominant ones. 77 odor-causing compounds were detected in source water samples, and about 40 compounds were associated with emerging chemical pollution, including ethers, cyclic acetals, phenols, and benzene-containing compounds, etc. 2-Methylisoborneol was identified as the main earthy/musty odor-causing compound and thioethers including dimethyl disulfide and dimethyl trisulfide were mainly associated with swampy/septic odor. In addition, some cyclic acetals were first detected in Huangpu River, which were the main cause of chemical odor episodes in Huangpu River source water. Cyclic acetals and bis(2-chloro-1-ethylethyl) ether could be associated with resin-related industrial pollution, and their potential health effects are also worthy of attention.
... HABs pose challenges to drinking water utilities and lake managers due to the toxic compounds that can be released upon lysis of the cells (Westrick & Szlag 2018). Blooms also often produce a variety of taste and odor (T&O) compounds, and while they are not usually a health concern, they can be problematic when it comes to consumer perception and satisfaction (Carniero et al. 2020, Dietrich & Burlingame 2014, Watson 2010. Both long-term and acute exposure to the neurotoxins and hepatotoxins produced by cyanobacteria can cause sickness and death, so it is important that drinking water utilities implement monitoring programs to track and treat HABs (Chorus & Welker 2021). ...
Key Takeaways
Flow imaging microscopy (FIM) combines a flow cytometer's fluidic architecture with a microscope's spatial resolution to allow morphometric analysis of objects in suspensions such as water.
FIM's real‐time analysis and identification of potential cyanotoxin producers help utilities understand population dynamics to maintain healthier source waters and reduce response times when a bloom is indicated.
Case studies show FIM's advantages and limitations in harmful algal bloom monitoring programs for reservoir management and water treatment.
... The unpleasant odor in algal oil is mostly caused by DHA oxidation, however, oxidation of other fatty acids also plays role (Wen et al. 2022). High PUFA concentrations in diatoms, Chrysophytes and Synurophytes results in the production of volatile organic compound derivatives with fishy odor and cucumber smelling (oxylipins) odor upon cell rupture (Watson 2010). Natural or synthetic antioxidants are added to enhance the stability of algal oil. ...
Omega-3 fatty acids have gained attention due to numerous health benefits. Eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) are long chain omega-3 fatty acids produced from precursor ALA (α-linolenic acid) in humans but their rate of biosynthesis is low, therefore, these must be present in diet or should be taken as supplements. The commercial sources of omega-3 fatty acids are limited to vegetable oils and marine sources. The rising concern about vegan source, fish aquaculture conservation and heavy metal contamination in fish has led to the search for their alternative source. Microalgae have gained importance due to the production of high-value EPA and DHA and can thus serve as a sustainable and promising source of long chain omega-3 fatty acids. Although the bottleneck lies in the optimization for enhanced production that involves strategies viz. strain selection, optimization of cultivation conditions, media, metabolic and genetic engineering approaches; while co-cultivation, use of nanoparticles and strategic blending have emerged as innovative approaches that have made microalgae as potential candidates for EPA and DHA production. This review highlights the possible strategies for the enhancement of EPA and DHA production in microalgae. This will pave the way for their large-scale production for human health benefits.
... In turn, the sulfides are themselves affected by the pH of the water (Buerkens et al. 2020). Watson (2010) provides a comprehensive list of these odorous compounds. The fishy odors in untreated surface waters can range from cod liver oil-like, clam shells, dead crab, rotten fish, ammoniacal, to fishy (Suffet et al. 1996), and thus could be affected by changes in pH. and within some green algae. ...
There is general agreement that pH is an important parameter in many drinking water treatment and control processes such as taste and odor (T&O) control. However, pH is not usually targeted as a primary control parameter and its effects on T&O are often overlooked in favor of other treatment issues. When it comes to T&O control, treatment alternatives typically focus on oxidation and adsorption processes. Whether within these processes or separately, pH plays an important role and the effects on T&O should be considered. For example, pH plays a role in the speciation of odorous chemicals in the environment, some of which arise in wastewater treatment and others from the occurrence of metals in water. During blooms of algae and cyanobacteria in surface water, pH is an important parameter affecting water quality and T&O. Finally, as pH is important for the sample preservation and analysis of T&O compounds, pH is important in the fate and control of T&O. The objective of this article is to better understand the various ways that pH can influence T&O production, control, and analysis of odorants in water and encourage advancement in the state of the science of pH optimization for T&O control.
... The list of volatile organic compounds (VOC) produced by the bloom species is extensive. A summary of the 30+ specific VOCs can be found in Watson (2010) and are summarized in Table 1. Many descriptive terms have been used to characterize chrysophyte T&O: ammonia, black currant leaves, earthy, fishy, flowery, fresh, fruity, garlic, green-leafy, herbaceous, honey, lavender, mushroom, orange, orange-rose, putrid, rancid, rotten fish, septic, smoky/moldy, swampy, sweet, and tobacco. ...
... Trace concentrations of various odorous metabolites produced by bacteria may change the organoleptic properties of water and act as chemical attractants or repellents in the aquatic food web for invertebrates, fish, and humans (Höckelmann et al., 2004;Watson et al., 2007). In freshwater environments, Cyanobacteria have been known as the major producers of odorants Watson, 2010;Watson et al., 2008). Off-flavor compounds, such as MIB and GSM, which deteriorate the quality of water, are often associated with seasonal blooms of Oscillatoria, Anabaena flos-aquae, Planktothrix, and Microcystis aeruginosa (Hayes & Burch, 1989;Li et al., 2007;Su et al., 2015), where decaying blooms can release many odorous metabolites (Ma et al., 2013;Smith et al., 2008) and other bioactive compounds like cyanotoxins (Smith et al., 2008). ...
Occurrences of odorous bacterial metabolites, 2‐methylisoborneol (MIB) and geosmin (GSM), in drinking water supply reservoirs are considered as a nuisance by the water industry and a source of
complaints from customers. In Eagle Creek Reservoir, routine monitoring programs of MIB and GSM highlight intense odorous outbreaks during the spring season when high inflow discharges occur. Cyanobacteria have always been assumed to be source of these metabolites even if no known producers are present in raw water. A copper‐based algaecide is often used to terminate the metabolite production and the algal growth in the reservoir. The current study was designed to investigate and identify other biological
sources involved in the biosynthesis of MIB and GSM metabolites as well as environmental factors that could be important triggers for the growth of bacterial producers. The community structure of the bacterioplankton was determined using a 16S rRNA gene sequencing technique, which showed that not only Cyanobacteria but Actinobacteria also were involved in the reservoir internal production. Planktothrix species was identified as the main source of GSM (p < 0.001) while Streptomyces (Actinobacteria) was very likely responsible of MIB (p < 0.01). Application of an algaecide disrupted GSM and the growth of Planktothrix but was less effective against MIB and Streptomyces. Statistical analyses revealed that MIB‐ and GSM-causing bacteria were found abundant when the water was enriched with nitrogen, temperature cooler, and the water column mixed.
The recovery of bioactive products with green processes is a critical topic for the research and industry fields. In this work, the application of solid–liquid (SLE), microwave-assisted extraction (MAE) with aq. ethanol 90% v/v and supercritical fluid extraction (SFE) with CO2 for the recovery of biocomponents from Scenedesmus obliquus is studied. The effects examined were temperature (30–60 °C), time (6–24 h), and solvent-to-biomass ratio (20–90 mLsolv/gbiom) for SLE, temperature (40–60 °C), time (5–25 min), solvent-to-biomass ratio (20–90 mLsolv/gbiom), and microwave power (300–800 W) for MAE, and temperature (40–60 °C), pressure (110–250 bar), solvent flow rate (20–40 gsolv/min), and cosolvent presence (0, 10% w/w ethanol) for SFE in relation to the extract’s yield, phenolic, chlorophyll, carotenoid content, and antioxidant activity. The optimum extraction conditions determined were 30 °C, 24 h, and 90 mLsolv/gbiom for SLE, 60 °C, 5 min, 90 mLsolv/gbiom, and 300 W for MAE, and 60 °C, 250 bar, and 40 gsolv/min for SFE. Additionally, a kinetic SFE study was conducted and the obtained results were satisfactorily correlated using Sovová’s model. The comparison between the methods proved MAE’s efficiency in all terms compared to SLE. Moreover, SFE was accompanied with the lowest yield and chlorophyll content, yet led to an increased carotenoid content and improved antioxidant activity. Finally, the cosolvent addition significantly improved SFE’s yield and led to the most superior extract.
The production of bioactive products from microalgae biomass with efficient and environmentally friendly technologies is a field of great research interest. The present work focuses on the recovery of high-added value bioactive components from Chlorella vulgaris through microwave-assisted extraction (MAE) with aq. ethanol 90% v/v. The effect of extraction temperature (40–60 °C), duration (5–25 min), solvent-to-biomass ratio (20–90 mLsolv/gbiom), and microwave power (300–800 watts) was investigated regarding the extraction yield, extract’s chlorophyll, carotenoid and phenolic content, and antioxidant activity. MAE optimization at 60 °C, 300 watts, 14 min, and 22 mLsolv/gbiom led to 11.14% w/w yield, 63.36 mg/gextr total chlorophylls, 7.06 mg/gextr selected carotenoids of astaxanthin, lutein and β-carotene, 24.88 mg/gextr total carotenoids, 9.34 mgGA/gextr total phenolics, and 40.49 mgextr/mgDPPH IC50 (antioxidant activity indicator). Moreover, the conventional solid-liquid extraction (SLE) with aq. ethanol 90% v/v, the supercritical fluid extraction (SFE) with CO2, as well as SFE with cosolvent addition (10% w/w ethanol), were also performed for comparison purposes. The results revealed that SLE presented the highest yield. However, the non-conventional methods of MAE and SFE led to extracts of competitive or even better quality under significantly shorter extraction duration.
Microalgae are well-known for their high-added value compounds and their recovery is currently of great interest. The aim of this work is the recovery of such components from Chlorella vulgaris through supercritical fluid extraction (SFE) with CO2. The effect of the extraction temperature (40–60 °C), pressure (110–250 bar), and solvent flow rate (20–40 g/min) was tested on yield, the extract’s antioxidant activity, and the phenolic, chlorophyll and carotenoid content. Thus, data analysis indicated that the yield was mainly affected by temperature, carotenoids by pressure, while the extract’s phenolics and antioxidant activity were affected by the synergy of temperature and pressure. Moreover, SFE’s kinetic study was performed and experimental data were correlated using Sovová’s mass transfer-based model. SFE optimization (60 °C, 250 bar, 40 g/min) led to 3.37% w/w yield, 44.35 mgextr/mgDPPH antioxidant activity (IC50), 18.29 mgGA/gextr total phenolic content, 35.55, 21.14 and 10.00 mg/gextr total chlorophyll, carotenoid and selected carotenoid content (astaxanthin, lutein and β-carotene), respectively. A comparison of SFE with conventional aq. ethanol (90% v/v) extraction proved SFE’s superiority regarding extraction duration, carotenoids, antioxidant activity and organoleptic characteristics of color and odor despite the lower yield. Finally, cosolvent addition (ethanol 10% w/w) at optimum SFE conditions improved the extract’s antioxidant activity (19.46%) as well as yield (101.81%).
ResearchGate has not been able to resolve any references for this publication.