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    Effects of the consumption of algal biomass versus protein concentrate on postprandial satiety and metabolism
    (Elsevier BV, 2024-12) Wu JY; Tso R; Yong YN; Lim SPS; Wheeler T; Nag A; Cheng L; Talukder MMR; Huffman L; Quek SY; Leow MKS; Haldar S
    Algae are promising sources of nutritious and sustainable protein, but little is known about their metabolic health impact and acceptability as meal ingredients. This acute, randomized, controlled, five-way crossover trial compared whole algal biomasses and their corresponding protein concentrates to soy protein concentrate in terms of palatability, appetite, satiety, and metabolic response. Nineteen healthy Chinese males (21–50 years, 18.5–25.0 kg/m2) consumed noodle meals supplemented with 10 g of nori biomass/protein concentrate (NB/NC), Chlorella vulgaris biomass/protein concentrate (CB/CC) or soy protein concentrate control (CON) in randomized order. At regular intervals, blood samples were collected to measure biochemical markers, while gastrointestinal tolerance, palatability, and appetite were assessed using questionnaires and visual analog scales (VAS). Results indicated that algae-enriched meals were well-tolerated and comparable to soy in both visual appeal and smell, with NB and CC outperforming soy in aftertaste (p < 0.05). There were no significant differences between treatments in glucose, insulin, C-peptide, appetite/satiety, plasma ghrelin, and GLP-1. However, exploratory analysis of serum triglycerides revealed significant time × treatment effects (p < 0.004) and differences in incremental area under the curve (iAUC0–120 p = 0.0249). Our findings reveal that algal biomasses and protein concentrates are as comparable to soy protein concentrate in palatability, satiety, and metabolic outcomes, highlighting their potential as practical, sustainable, and nutritious ingredients.
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    Elevating phosphorus accumulation in waste stabilisation pond algae : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Environmental Engineering at Massey University, Palmerston North, New Zealand
    (Massey University, 2019) Sells, Matthew
    Facultative waste stabilisation ponds (WSP) are used globally for wastewater treatment due to their low cost and simple operation. While WSPs can be effective at removing organic pollutants and pathogens, phosphorus removal is typically poor. Algae that are common in WSPs are known to accumulate phosphorus and increase their phosphorus content in the biomass from 1% up to 3.8% (gP/gSS), which is believed to be from the production of intracellular polyphosphate granules. This phenomenon, known as luxury uptake, may be possible to manipulate to improve phosphorus removal in WSPs; however, its occurrence is sporadic and poorly understood. This PhD thesis was undertaken to investigate the conditions that influence phosphorus accumulation in WSP algae. Phosphorus accumulation was quantified using two methods: (1) the traditional phosphorus content in the biomass (gP/gSS), and (2) a new image analysis method developed in this thesis that quantifies stained polyphosphate granules within individual algal cells (μm2 granule/μm2 cell). Following a literature review and screening experiments that sought to identify variables that could affect the phosphorus content in the biomass (gP/gSS), six variables: temperature, phosphorus concentration, light intensity, mixing intensity, organic load, and pH were comprehensively examined using 40 batch factorial experiments (26-1) and a mixed genus culture from a full-scale WSP. Nine variables and interactions had a significant effect on the phosphorus content in the biomass and were incorporated into a regression equation. This ‘mixed genus’ regression equation was tested against literature data, where seven out of the eight batch experiments from the literature were successfully predicted. In order to identify if the batch findings could be applied to a continuous process, which is more typical of full-scale WSPs, a bench-scale novel ‘luxury uptake’ process was designed, built, and operated under five different scenarios. The regression equation successfully predicted the experimental results for three of the five conditions examined. It was theorised that differences in behaviour at the genus level might explain why all five conditions were not successfully predicted. In an attempt to improve the prediction capability, the ‘black-box’ of mixed genus analysis was ‘opened’ to allow the effects of variables on phosphorus accumulation at the genus level to be directly examined. To achieve this, a new image analysis method was developed that quantified stained polyphosphate granules in individual algal cells. To ensure the granules being measured were indeed polyphosphate, algal cells were analysed using transmission electron microscopy coupled with energy dispersive X-ray spectroscopy, which confirmed the granules contained higher levels of phosphorus compared to the remaining cell. The image analysis method was then used to quantify stained polyphosphate granules in individual cells from the 40 batch factorial experiments mentioned previously. The results using the image analysis method showed that, for the five most abundant algal genera, Micractinium/Microcystis had the highest average accumulation of polyphosphate granules (17% μm2 granule/μm2 cell), followed by Scenedesmus (12%), Pediastrum (11%), Monoraphidium (8%), and Actinastrum (4%). Although none of the genera studied had the same combination of significant variables, all five genera preferred a high phosphorus concentration to elevate polyphosphate granule accumulation. Furthermore, a high light intensity, high organic load, or high temperature was preferred by the algae if the variable was significant for that genus. The culture used in the bench-scale continuous flow ‘luxury uptake’ process originated from a mixed genus WSP culture; however, it had become dominated by the Scenedesmus genus. Therefore, the regression equation was refined to use the batch data for this genus alone. This new Scenedesmus regression equation was compared against the experimental data from the ‘luxury uptake’ process previously mentioned. Polyphosphate granule accumulation was now successfully predicted in all five experimental conditions at the 95% confidence level. This improved prediction capability indicates that an understanding of the algal genus present in a WSP system is required for accurate predictions of the phosphorus accumulation to be obtained, and the batch data can indeed be applied to a continuous process. An unexpected result of the research was that, contrary to what was believed in the literature, an increase in the phosphorus content in the biomass did not necessarily increase the polyphosphate granule accumulation. Further examination identified that individual cells from the same algal species had varying polyphosphate granule contents from 0% to over 20% (μm2 granule/μm2 cell) when exposed to the same conditions. This variation was hypothesised to be from cellular functions influencing the granules differently depending on the individual alga’s cell cycle. In addition, when the phosphorus content in the biomass was increased above 2.1% (gP/gSS), no significant effect on the average quantity of polyphosphate granules was observed. This finding indicates that other forms of phosphorus storage must be responsible for attaining a highly elevated phosphorus content in the biomass.
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    Photobioreactor production of microalgae for potential fuel oils : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biotechnology at Massey University, Palmerston North, New Zealand
    (Massey University, 2013) Luangpipat, Tiyaporn
    This work focussed on a detailed characterization of the freshwater microalga Chlorella vulgaris as a producer of potential fuel oils. Uniquely, growth and oil production of C. vulgaris were characterized in full strength seawater-based media, something that has not been previously reported. C. vulgaris was selected for a detailed study after a screening of six potential oil producing microalgae. For photoautotrophic growth, always under carbon sufficiency and at normal growth temperature, the characterization study covered: the biomass growth rate; lipid content in the biomass; productivities of the lipids and the biomass; the biomass loss in the dark; the lipid/biomass yields on macronutrients; and the energy content of the biomass. The above key production parameters were characterized in a purpose-built tubular photobioreactor (~80 L) and in stirred tank photobioreactors (~7.5 L) under conditions of nitrogen sufficiency and at various levels of nitrogen limitation. Production was evaluated in both batch and continuous cultures at various dilution rates using indoor light to mimic sunlight. The production temperature mimicked the relatively warm conditions that would be encountered in a potential production system located outdoors in a tropical climate. In seawater media at 25–27 °C, C. vulgaris was shown to have a crude oil productivity of >37 mg L⁻¹ d⁻¹ and the energy content of the biomass could exceed 25 kJ g⁻¹, depending on the culture conditions. Both these values were high compared with the reported data for this alga in freshwater media. Compared with continuously illuminated culture, day–night cycling of irradiance reduced oil productivity by ~31%, but the energy content of the biomass were reduced by only about 8%. In seawater, the alga could be grown as rapidly and stably as in freshwater. The lipid content of the biomass commonly exceeded 30% by dry weight and in exceptional cases a lipid content of more than 50% (by weight) was achieved. Biomass calorific values of ≥27 kJ g⁻¹ could be attained in some cases. Nitrogen starvation enhanced the lipid contents of the biomass by >3-fold relative to the lipid contents for the nonstarved case. Steady-state continuous cultures were shown to be possible. Both batch and continuous operations were feasible, especially in stirred tanks, but the culture was more failure prone, or relatively less productive, in the tubular photobioreactor.
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    Prymnesiophytes of New Zealand's coastal waters : taxonomy, physiology and ecology : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Biology and Biotechnology at Massey University
    (Massey University, 1994) Rhodes, Lesley Louise; Rhodes, Lesley Louise
    Prymnesiophytes are an important component of the marine phytoplankton of New Zealand coastal waters, but there is little knowledge of the taxonomy, physiology or ecology of local strains. The Class comprises four orders which contain putative families and genera of the microscopic organisms, the microalgae. The Prymnesiophytes are known for their ability to explode in population numbers into "blooms"; one of New Zealand's most common bloom-formers is the coccolithophore Emiliania huxleyi (Prymnesiophyceae), which dominated the extensive phytoplankton blooms observed around New Zealand's coastline during 1993 - 94. Aspects of the physiology of and factors contributing to bloom formation in E.huxleyi are investigated. The phenomenon of seasonal blooms, a common occurrence amongst the microalgae, is reviewed. Studies of the blooms which occurred along the north-east coastline of New Zealand in 1992-93 showed that these were unusual events that were linked to the climatic conditions at that time, in particular cold sea temperatures associated with an "El-Niño" phase of the Southern Oscillation Index in the southern Pacific Ocean. The dominant microalgae were Gephyrocapsa oceanica (Prymnesiophyceae) and Fibrocapsa japonica (Raphidophyceae) and it is probable that the conditioning of the coastal waters by these microalgae had a role in the succeeding toxic event, in which human illnesses were definitively linked to shellfish toxins due to microalgae for the first time in New Zealand. Allelopathic, or chemical, interactions between microalgae were investigated in this study and Prymnesium parvum and P.patellifera caused inhibition of the growth of species from several microalgal classes. Unfortunately P.patellifera rapidly lost its inhibitory activity in vitro, but P.parvum remained active for several years in culture and was therefore selected as a positive control for the bioassays for ichthyotoxicity that were developed. The class Prymnesiophyceae includes toxic species of three genera, namely Chrysochromulina, Prymnesium and Phaeocystis. Ichthyotoxin bioassays based on toxin sensitive microalgae (Chattonella antiqua and Heterocapsa triquetra), shellfish larvae (Haliotis iris), brine shrimps (Artemia salina) and salmon erythrocytes (Oncorhynchus tshawytscha) were developed or refined and evaluated to enable the rapid and inexpensive detection of the haemolytic and cytolytic prymnesiophyte toxin, prymnesin. The novel quadriflagellate species C.quadrikonta, which bloomed in north-east New Zealand, May 1994, exhibited low levels of haemolytic activity in stationary phase cultures grown in standard nutrient medium (at 18°C, 100 μmol m-2s-1) as determined by the erythrocyte assay; no other Chrysochromulina species tested was toxic. Six locally occurring species were identified by electron microscopic examination of scales and light and electron microscopic observation of cultured isolates in this study. Seventeen of the nearly fifty named species of Chrysochromulina have now been identified in New Zealand. The average cell sizes and unmineralised spine scale lengths of the New Zealand isolates of C.ericina, C.hirta and C.quadrikonta were slightly larger than for their type species and the calcareous scales of E.huxleyi and G.oceanica were more heavily calcified than their northern hemisphere counterparts. No gradation of calcification with increased latitude was observed for the coccolithophores, as had been noted previously, and this might reflect the consistently lower sea temperatures prevailing, due to the unusually protracted "El-Niño" climatic conditions. Fluorescent probes proved to be useful tools for the differentiation of some morphologically-like species under the light microscope: Calcofluor white helped distinguish between cells of C.ericina and C.quadrikonta. The differentiation of the genera Prymnesium and Chrysochromulina was enabled through the specific binding of fluorescently-tagged wheat germ lectin to Chrysochromulina species. The growth characteristics and cultural idiosyncrasies of several southern hemisphere Chrysochromulina isolates have been described and compared with the toxic northern hemisphere relative, C.polylepis. C.polylepis, C.ericina and C. hirta fell into a temperate group on the basis of optimum growth rates (doublings d-1), while C.acantha, C.apheles, C.camella and C.quadrikonta fell into a sub-tropical group. All but C.acantha grew equally well with potassium nitrate, urea or ammonium chloride; C.acantha grew significantly slower with urea as nitrogen source. Only C.quadrikonta had a selenium requirement for growth. Maximum growth rates (doublings d-1) recorded in vitro were C.acantha, 1.2; C.apheles, 0.9; C.camella, 1.1; C.ericina, 1.5; C.hirta, 2.4 and C.quadrikonta, 1.4. The Chrysochromulina species and E.huxleyi and G.oceanica grew at low light intensities (25 μmol m-2 s-1), which could give these prymnesiophytes a competitive advantage in bloom situations, where shading due to the phytoplankton biomass can occur. The New Zealand isolate of G.oceanica grew optimally at salinities of 17 - 29°/oo, pH of 8.4 - 8.9 and temperatures of 20 – 25°C; E.huxleyi grew optimally at 29°/oo, pH7.5 - 8.9 and 15 – 25°C. G.oceanica grew equally well with ammonium chloride, urea or nitrate as nitrogen source; E.huxleyi grew optimally with ammonium chloride. Maximum growth rates recorded were 1.9 doublings d-1 for E.huxleyi and 1 4 doublings d-1 for G.oceanica.