In vitro evaluation of the antimethanogenic potency and effects on fermentation of individual and combinations of marine macroalgae

Contribution of ruminants to total greenhouse gas emissions in Australia is approximately 10% and likely to increase with demand for livestock products, thus an efficient method of mitigation must be implemented. The red marine macroalgae Asparagopsis taxiformis reduces enteric methane production by up to 99% in vitro. Other macroalgae with less potent antimethanogenic properties may complement inclusion of Asparagopsis in livestock feeds. Adoption of environmental based changes in livestock systems must provide benefits to producers if change in management is to be adopted. This study used 72 h in vitro fermentations with rumen inoculum to characterize and rank seven species of macroalgae at low inclusion that previously demonstrated some degree of antimethanogenesis at higher inclusion concentration. The seven were assessed at 5% inclusion (OM basis) and in combination with Asparagopsis to evaluate beneficial effects on fermentation. When tested individually, improvements in volatile fatty acids were generally observed, however, minimal effect on gas production and no clear justification for a ranking order were demonstrated. When tested in combination with Asparagopsis, the effects on fermentation were dominated by presence of Asparagopsis at 2% and no further benefits demonstrated. Therefore, Asparagopsis remains the only macroalga inducing near elimination of methane in vitro and benefit of combinations with other macroalgae evaluated in this study was not demonstrated. However, combination with high protein macroalgae is proposed to provide productivity enhancement during seasonal lows in grass quality and thus reduce methane emissions intensity providing a stronger conduit for environmental responsibility while increasing productivity

In vitro evaluation of the antimethanogenic potency and effects on fermentation of individual and combinations of marine macroalgae

Contribution of ruminants to total greenhouse gas emissions in Australia is approximately 10% and likely to increase with demand for livestock products, thus an efficient method of mitigation must be implemented. The red marine macroalgae Asparagopsis taxiformis reduces enteric methane production by up to 99% in vitro. Other macroalgae with less potent antimethanogenic properties may complement inclusion of Asparagopsis in livestock feeds. Adoption of environmental based changes in livestock systems must provide benefits to producers if change in management is to be adopted. This study used 72 h in vitro fermentations with rumen inoculum to characterize and rank seven species of macroalgae at low inclusion that previously demonstrated some degree of antimethanogenesis at higher inclusion concentration. The seven were assessed at 5% inclusion (OM basis) and in combination with Asparagopsis to evaluate beneficial effects on fermentation. When tested individually, improvements in volatile fatty acids were generally observed, however, minimal effect on gas production and no clear justification for a ranking order were demonstrated. When tested in combination with Asparagopsis, the effects on fermentation were dominated by presence of Asparagopsis at 2% and no further benefits demonstrated. Therefore, Asparagopsis remains the only macroalga inducing near elimination of methane in vitro and benefit of combinations with other macroalgae evaluated in this study was not demonstrated. However, combination with high protein macroalgae is proposed to provide productivity enhancement during seasonal lows in grass quality and thus reduce methane emissions intensity providing a stronger conduit for environmental responsibility while increasing productivity

The future of aquatic protein: implications for protein sources in aquaculture diets

Approximately 70% of the aquatic-based production of animals is fed aquaculture, whereby animals are provided with high-protein aquafeeds. Currently, aquafeeds are reliant on fish meal and fish oil sourced from wild-captured forage fish. However, increasing use of forage fish is unsustainable and, because an additional 37.4 million tons of aquafeeds will be required by 2025, alternative protein sources are needed. Beyond plantbased ingredients, fishery and aquaculture byproducts and insect meals have the greatest potential to supply the protein required by aquafeeds over the next 10–20 years. Food waste also has potential through the biotransformation and/or bioconversion of raw waste materials, whereas microbial and macroalgal biomass have limitations regarding their scalability and protein content, respectively. In this review, we describe the considerable scope for improved efficiency in fed aquaculture and discuss the development and optimization of alternative protein sources for aquafeeds to ensure a socially and environmentally sustainable future for the aquaculture industry

A new method to examine the oberhautchen of lizard skin

Scanning electron microscopy (SEM) is a powerful tool used in the study of lizard skin morphology and has allowed researchers to gain insight into the intricate structure of complex epidermal layers, an interesting part of which is the outer layer or oberhautchen. Methods involved in the preparation of samples for SEM are invasive and usually involve killing and preserving specimens. Here we present a new, simple, highly accurate method for the examination of living lizard epidermis using polyvinylsiloxane impression material and epoxy resin to create molds. We created molds of live Oedura castelnaui (Squamata: Diplodactylidae) using two different types of epoxy resin to compare their efficacy. Viscosity was the important factor determining whether there were artifacts in the mold, and the resin that created fewest artifacts was Epirez 123® (ITW Polymers & Fluids). We used Epirez 123® to create molds of Phyllurus ossa, P. amnicola, and Nephrurus levis (Squamata: Carphodactylidae), which all have ornate oberhautchen. We visually compared these with published images of hair sensors of congeners, and found that our method compared very favorably. Thus, this method can produce exceptional quality reproductions of complex microornamentations within the oberhautchen of living lizards

A comparative assessment on how molasses and CO2 gas prevent carbon limitation in the large-scale culture of freshwater macroalgae

Freshwater macroalgae are an attractive treatment option for waste streams that have very high concentrations of nutrients. However, the long water residence times required in these scenarios will result in carbon becoming a limiting nutrient that negatively impacts the rate of biomass productivity and, subsequently, the potential for nutrient uptake. This study examined how the rate of carbon supplementation influenced the biomass productivity of Oedogonium intermedium, during both winter and summer periods in high rate algal ponds (HRAPs) maintained under batch conditions. We also examined the novel use of molasses as a source of carbon for intensive algal cultures and compared its effect on biomass productivity to that of CO2 gas. Oedogonium intermedium responded positively to carbon supplementation from both molasses and CO2 gas, with biomass productivity increasing as the rate of carbon supplementation increased. In cultures with no carbon supplementation, the average productivity of O. intermedium was 2.2 (+/- 0.8) g m(-2) day(-1), and a maximum of 17.3 g m(-2) day(-1) and 20.8 g m(-2) day(-1) during summer when carbon was supplemented through the addition of molasses and CO2, respectively. The optimal rate of carbon supplementation was 0.06 g of carbon per liter (g (C) L-1) in winter and 0.08 g (C) L-1 during summer. The addition of an exogenous source of carbon resulted in a decline in the culture pH and increased the availability of the dissolved inorganic carbon (DIC) pool and subsequently, carbon uptake by the algae. This study has identified a novel method to supplement carbon to algal cultures, where the waste residue from the sugar industry can be used as viable source of inorganic carbon. Importantly, we have demonstrated that O. intermedium can be cultivated in HRAPs without requiring a high rate of water exchange, providing that its requirements of DIC are satisfied

Plant growth-promoting properties of extracts produced by fermenting the freshwater macroalga, Oedogonium intermedium

Extracts produced from marine macroalgal biomass promote plant growth, improve yield, and increase the tolerance of plants to physiological stressors. Most of these extracts are produced with dried macroalgal biomass as their stock material, and use processing techniques that cause considerable modification to the original biomass and require a substantial investment in energy and equipment. As such, the aim of this study was to determine whether the freshwater macroalga Oedogonium intermedium could be successfully fermented using freshly harvested biomass, such that this biomass was transformed into a stable, non-offensive product that had plant growth-promoting properties. This was demonstrated by manipulating the starting conditions (presence or absence of salinity, molasses, and microbes) of the fermentations. The liquid extracts had a positive effect on the growth of mung bean plants compared with the positive controls – a soluble plant fertiliser and a commercially available fermented seaweed product. The most effective extract (Oedo 4), which was fermented in 20 ppt saltwater with the addition of molasses, demonstrated a 28.9–48.6% larger total plant dry weight than the commercial controls, respectively. Notably, extracts fermented in 20 ppt saltwater resulted in larger quantities of N, P, K, Ca, and Fe than those fermented in freshwater, while extracts fermented with molasses had the lowest final pH (<4), resulting in a stable extract with non-offensive odours that were not particularly strong. This study demonstrates the viability of producing fermented extracts directly from the freshly harvested biomass of a freshwater macroalga, and that those extracts have plant growth-promoting properties

The effects of concentration and supplementation time of natural and synthetic sources of astaxanthin on the colouration of the prawn Penaeus monodon.

The purpose of this study was to quantify and model the combined effects of dietary concentration of astaxanthin (32.5–102.5 ppm) and time of supplementation (29–69 days) on the growth, survival, and colouration of Penaeus monodon (Black tiger prawn), using natural (Haematococcus pluvialis) and synthetic (Carophyll Pink®) astaxanthin. A model was used to determine the optimal combination of concentration and supplementation time required to obtain a commercial colour standard, based on the minimum quantity of astaxanthin required for each source. The provision of astaxanthin, as either natural or synthetic, at any concentration or supplementation time, had no effect on growth or survival. However, the colour of boiled prawns supplemented with natural astaxanthin had a small, but significant, improvement in colour (CIE2000 L*a*b* colour distances between 0.74 ± 0.22 and 1.79 ± 0.63), when compared with supplementation with synthetic astaxanthin. The astaxanthin concentration and supplementation time also had a significant effect on the colour of boiled prawns, where higher concentrations of astaxanthin for longer supplementation times resulted in improved colouration up until a plateau of 98 ppm for 66 days for natural astaxanthin, and 90 ppm for 63 days for synthetic astaxanthin. An additional model was used to predict the minimum usage of astaxanthin for each source during three annual commercial production cycles (Christmas, Summer, and Restock). Compared with the current commercial standard, the natural source would require 21.0%, 21.6%, and 21.3% less total astaxanthin, and the synthetic source would require 0.7%, 0.2%, and 0.3% less total astaxanthin, for the Christmas, Summer, and Restock production cycles, respectively. The predictive models developed here were able to explain the combined effects of dietary concentration of astaxanthin, time of supplementation, and effects of source on the colouration of boiled prawns, thereby predicting the minimum usage required at the commercial pond scale

Maximising the productivity of the attached cultivation of Ulva tepida in land-based systems

The viability of land-based seaweed cultivation is linked to high areal productivity of biomass and best suited for species that grow vegetatively and unattached. To develop optimised strategies for cultivation in land-based systems for attached species characterised by short growth cycles with periodic reproduction, ropes were seeded with zoids of the green seaweed Ulva tepida and stacked vertically in the water column from one to four layers deep. The layers spanned a culture depth from 50 to 350mm below the surface of the water. After an initial grow-out period of 10 days, the biomass was continuously harvested on a rolling 4-day cycle which maintained the biomass in an actively growing state, over the 62-day cultivation period. Compared with the single layer treatment the vertical stacking of seeded ropes, in combination with frequent harvesting, increased the areal productivity of U. tepida by 40% with productivities>20 g dwm−2 day−1. Notably, productivities were similar between stacking treatments with two, three, or four layers due to a decreasing availability of light with an increasing number of layers and an increasing depth in the water column. Consequently, the most effective method of cultivation was to stack two layers of ropes in combination with the vertical movement of the layers through the water column with frequent harvesting to reduce the onset of reproduction

Maximising the productivity of the attached cultivation of Ulva tepida in land-based systems

The viability of land-based seaweed cultivation is linked to high areal productivity of biomass and best suited for species that grow vegetatively and unattached. To develop optimised strategies for cultivation in land-based systems for attached species characterised by short growth cycles with periodic reproduction, ropes were seeded with zoids of the green seaweed Ulva tepida and stacked vertically in the water column from one to four layers deep. The layers spanned a culture depth from 50 to 350mm below the surface of the water. After an initial grow-out period of 10 days, the biomass was continuously harvested on a rolling 4-day cycle which maintained the biomass in an actively growing state, over the 62-day cultivation period. Compared with the single layer treatment the vertical stacking of seeded ropes, in combination with frequent harvesting, increased the areal productivity of U. tepida by 40% with productivities>20 g dwm−2 day−1. Notably, productivities were similar between stacking treatments with two, three, or four layers due to a decreasing availability of light with an increasing number of layers and an increasing depth in the water column. Consequently, the most effective method of cultivation was to stack two layers of ropes in combination with the vertical movement of the layers through the water column with frequent harvesting to reduce the onset of reproduction

The effects of concentration and supplementation time of natural and synthetic sources of astaxanthin on the colouration of the prawn Penaeus monodon.

The purpose of this study was to quantify and model the combined effects of dietary concentration of astaxanthin (32.5–102.5 ppm) and time of supplementation (29–69 days) on the growth, survival, and colouration of Penaeus monodon (Black tiger prawn), using natural (Haematococcus pluvialis) and synthetic (Carophyll Pink®) astaxanthin. A model was used to determine the optimal combination of concentration and supplementation time required to obtain a commercial colour standard, based on the minimum quantity of astaxanthin required for each source. The provision of astaxanthin, as either natural or synthetic, at any concentration or supplementation time, had no effect on growth or survival. However, the colour of boiled prawns supplemented with natural astaxanthin had a small, but significant, improvement in colour (CIE2000 L*a*b* colour distances between 0.74 ± 0.22 and 1.79 ± 0.63), when compared with supplementation with synthetic astaxanthin. The astaxanthin concentration and supplementation time also had a significant effect on the colour of boiled prawns, where higher concentrations of astaxanthin for longer supplementation times resulted in improved colouration up until a plateau of 98 ppm for 66 days for natural astaxanthin, and 90 ppm for 63 days for synthetic astaxanthin. An additional model was used to predict the minimum usage of astaxanthin for each source during three annual commercial production cycles (Christmas, Summer, and Restock). Compared with the current commercial standard, the natural source would require 21.0%, 21.6%, and 21.3% less total astaxanthin, and the synthetic source would require 0.7%, 0.2%, and 0.3% less total astaxanthin, for the Christmas, Summer, and Restock production cycles, respectively. The predictive models developed here were able to explain the combined effects of dietary concentration of astaxanthin, time of supplementation, and effects of source on the colouration of boiled prawns, thereby predicting the minimum usage required at the commercial pond scale