Marianne Su-Ling Brooks

Heterotrophic and mixotrophic cultivation of microalgae for biodiesel production in agricultural wastewaters and associated challenges—a critical review

Many studies have demonstrated that heterotrophic and mixotrophic growth for various microalgae species yields greater biomass and lipid content as compared to photoautotrophic cultivation. This review explores the possibility of leveraging the natural ability of the microorganisms to metabolize carbon heterotrophically and mixotrophically in agricultural wastewaters. This has the potential advantage of improving the overall economics for the production of biodiesel and value-added biomolecules from microalgae, mitigating an existing waste stream and minimizing water requirements. However, there are a number of challenges and gaps in scientific knowledge that suggest a need for ongoing research in the area. In this review, specific focus is dedicated to the metabolic mechanisms, reported performances, and practical challenges that contribute to the uncertainty of employing agricultural wastewaters for heterotrophic and mixotrophic microalgae cultures.

Optimization of ultrasound-assisted extraction of anthocyanins from haskap berries (Lonicera caerulea L.) using Response Surface Methodology

Haskap berries (Lonicera caerulea L.) are a rich source of bioactive molecules. As such, the extraction of anthocyanins is important for the development of many value-added products and functional food ingredients. In this paper, the ultrasound-assisted extraction (UAE) of anthocyanins from haskap berries was investigated. Significant independent variables were screened and optimized using Plackett-Burman (PB) and Box-Behnken (BB) designs, respectively. The mathematical model showed a high coefficient of determination (R(2)=0.9396) and the optimum conditions for the extraction were as follows: liquid/solid ratio 25:1 (mL/g), solvent composition of 80% ethanol, addition of 0.5% formic acid, ultrasound bath temperature of 35°C for 20 min. Under these conditions, the total anthocyanin content of 22.73 mg cyaniding 3-glucoside equivalents (C3G)/g dry weight (DW) was consistent with the predicted response of 22.45 mg C3G/g DW from the model (mean error of 1.28%). Five anthocyanins were identified in the optimized extract, namely cyanidin 3,5-diglucoside, cyanidin 3-glucoside, cyanidin 3-rutinoside, pelargonidin 3-glucoside, and peonidin 3-glucoside. Thus, UAE is a suitable technique for the extraction of anthocyanins from haskap berries.

Medical waste management – A review

This paper examines medical waste management, including the common sources, governing legislation and handling and disposal methods. Many developed nations have medical waste legislation, however there is generally little guidance as to which objects can be defined as infectious. This lack of clarity has made sorting medical waste inefficient, thereby increasing the volume of waste treated for pathogens, which is commonly done by incineration. This review highlights that the unnecessary classification of waste as infectious results in higher disposal costs and an increase in undesirable environmental impacts. The review concludes that better education of healthcare workers and standardized sorting of medical waste streams are key avenues for efficient waste management at healthcare facilities, and that further research is required given the trend in increased medical waste production with increasing global GDP.

Haskap Berries (Lonicera caerulea L.)—a Critical Review of Antioxidant Capacity and Health-Related Studies for Potential Value-Added Products

Haskap berries commonly refer to fruits of Lonicera caerulea L., recognized by the Japanese aborigines as the “elixir of life.” Due to their recent arrival on the North American market, haskap berries have not yet been positioned among other berries and compared in terms of their phytochemical content. Haskap berries have higher ascorbic acid and anthocyanin content than other berries known for their health-promoting benefits, such as blueberries. In this article, we give a brief description of the phytochemical content and limitations of current methods used for their quantification, as well as a critical review of the techniques available to assess the antioxidant capacity of haskap extract in comparison to other berries. We then present results from recent studies with haskap extracts used in in vitro (bacterial and human cell cultures), preclinical trials (in animal models), and a first-in-human study to assess the implications for human health. Finally, we discuss current commercial products and the potential of encapsulation technology to preserve the bioactivity and increase stability of the extracts, thus creating a new range of value-added haskap products.

Nutrient and media recycling in heterotrophic microalgae cultures

In order for microalgae-based processes to reach commercial production for biofuels and high-value products such as omega-3 fatty acids, it is necessary that economic feasibility be demonstrated at the industrial scale. Therefore, process optimization is critical to ensure that the maximum yield can be achieved from the most efficient use of resources. This is particularly true for processes involving heterotrophic microalgae, which have not been studied as extensively as phototrophic microalgae. An area that has received significant conceptual praise, but little experimental validation, is that of nutrient recycling, where the waste materials from prior cultures and post-lipid extraction are reused for secondary fermentations. While the concept is very simple and could result in significant economic and environmental benefits, there are some underlying challenges that must be overcome before adoption of nutrient recycling is viable at commercial scale. Even more, adapting nutrient recycling for optimized heterotrophic cultures presents some added challenges that must be identified and addressed that have been largely unexplored to date. These challenges center on carbon and nitrogen recycling and the implications of using waste materials in conjunction with virgin nutrients for secondary cultures. The aim of this review is to provide a foundation for further understanding of nutrient recycling for microalgae cultivation. As such, we outline the current state of technology and practical challenges associated with nutrient recycling for heterotrophic microalgae on an industrial scale and give recommendations for future work.

Bioactive Encapsulated Powders for Functional Foods—a Review of Methods and Current Limitations

The incorporation of functional ingredients in food products is often limited by their taste and instability during processing and storage. Encapsulation techniques are commonly used to overcome these limitations and for the development of value-added products. Although different methods and materials are available, their selection will depend on the bioactive properties and the desired characteristics of the encapsulate and the final product. Physicochemical characteristics of encapsulates should be assessed and considered during all stages of food processing. Although a considerable body of literature has reported the encapsulation of bioactives, there is still a large gap between research and their application and commercialization into food products. The purposes of this review are to provide an overview of the current research on the encapsulation of bioactive components and methods used for their preparation, discuss relevant physicochemical characteristics that should be considered for the application of encapsulates into food products, and provide directions for future research.

Refractance Window™ drying of haskap berry--preliminary results on anthocyanin retention and physicochemical properties.

The goal of this work was to determine the anthocyanin retention and physicochemical properties of haskap powder prepared by Refractance Window™ (RW) drying. In general, the RW-dried powder particles had a smooth surface with similar thickness, consistent with the preparation method, and had a solubility of 75.63% in water. The RW-dried powder (consisting of 98% haskap berries) retained approximately 93.8% of anthocyanins from the original frozen fruits, as assessed by the pH-differential method. This result is in good agreement with HPLC analysis that indicated 92.9% retention. Three anthocyanins were identified in frozen berries and RW-dried powder: cyanidin 3-glucoside, cyanidin 3-rutinoside, and peonidin 3-glucoside. Surprisingly, cyanidin 3-rutinoside exhibited the lowest retention.

Inactivation Kinetics of Yeast Cells during Infrared Drying

In this study, aqueous yeast suspensions were used to investigate the effects of drying (in an infrared heating environment) on the survival of yeast. The processes were modeled mathematically using a range of kinetics rate equations. The model parameters for each kinetic rate expression were obtained using a Matlab optimization procedure and the more suitable models describing the inactivation processes were identified. In order to provide the data for model validation, experiments were conducted using freshly prepared yeast suspensions. Additional experiments were also performed that further demonstrate the protective effects of sucrose and skim milk solids on yeast survival during drying. The simple Arrhenius equation was found to be a good model for predicting yeast survival during the control experiments, when heat was applied without dehydration occurring. Models incorporating both temperature and moisture content were more effective in describing yeast inactivation during drying. The model that gave the best predictions included the drying rate and the rate of temperature change as variables; the predicted activation energy for yeast deactivation was closest to that obtained from heating-only experiments in comparison with the other models examined. The results from this work are discussed and future prospects are suggested.

Phenolic Analyses of Haskap Berries (Lonicera caerulea L.): Spectrophotometry Versus High Performance Liquid Chromatography

Haskap berries (Lonicera caerulea L.) are known for their high phenolics, anthocyanins, and antioxidant potential. The data on the phenolic profile of these fruits are lacking. In this study, the phenolic profiles of three haskap varieties; tundra, berry blue, and indigo gem grown in Nova Scotia, Canada were investigated for the first time using spectrophotometery and high-performance liquid chromatography. Berries were analyzed for total phenolic content/total reducing capacity, total anthocyanin content, and antioxidant potential (2,2-diphenyl-1-picrylhydrazyl radical scavenging activity). The total reducing capacity, total anthocyanin content, and 2,2-diphenyl-1-picrylhydrazyl values were 6.17–8.42 mg gallic acid equivalents/gram fresh weight, 4.49–6.97 mg cyanidin-3-glucoside equivalents/gram fresh weight, and 78.70–89.55%, respectively. The extracts were analyzed by reversed-phase diode array detector–high-performance liquid chromatography through a gradient elution using Synergi 4 µm Max-RP C12 column and the chromatograms were acquired at 520, 360, and 320 nm for athocyanins, flavonoids, and free phenolic acids, respectively. The identified anthocyanins were cyanidin-3-glucoside (82.81–91.99% of the total anthocyanins), cyanidin 3,5-di-glucoside (2.31–4.27%), cyanidin-3-rutinoside (1.54–9.20%), peonidin-3-O-glucoside (0.75–3.44%), and pelargonidin-3-glucoside (0.77–2.98%). Other flavonoids (quercetin-3-β-D-glucoside and quercetin-3-rutinoside) and free phenolic acids (chlorogenic and neochlorogenic) were also quantified.

Impact of extraction and processing conditions on betalains and comparison of properties with anthocyanins — A current review

The search for natural pigments has been driven by growing evidence indicating that synthetic colorants can cause deleterious health effects. Betalains, in addition to anthocyanins, have been proposed as an alternative to address this need. However, the incorporation of natural pigments poses some challenges to the food industry, such as reduced stability in comparison to their synthetic counterparts. Moreover, betalains are not well studied in comparison to anthocyanins and information about the effects of processing on their physicochemical properties and stability is scattered. Thus, this review will provide an overview of the recent research on the extraction and processing of betalains from natural sources, and comparison of their colorant and physicochemical properties with anthocyanins.