Defatted Microalgal Biomass Research Articles

Enhancing Bioenergy Production from the Raw and Defatted Microalgal Biomass Using Wastewater as the Cultivation Medium.

Improving the efficiency of using energy and decreasing impacts on the environment will be an inevitable choice for future development. Based on this direction, three kinds of medium (modified anaerobic digestion wastewater, anaerobic digestion wastewater and a standard growth medium BG11) were used to culture microalgae towards achieving high-quality biodiesel products. The results showed that microalgae culturing with anaerobic digestate wastewater could increase lipid content (21.8%); however, the modified anaerobic digestion wastewater can boost the microalgal biomass production to 0.78 ± 0.01 g/L when compared with (0.35-0.54 g/L) the other two groups. Besides the first step lipid extraction, the elemental composition, thermogravimetric and pyrolysis products of the defatted microalgal residues were also analysed to delve into the utilisation potential of microalgae biomass. Defatted microalgae from modified wastewater by pyrolysis at 650 °C resulted in an increase in the total content of valuable products (39.47%) with no significant difference in the content of toxic compounds compared to other groups. Moreover, the results of the life cycle assessment showed that the environmental impact (388.9 mPET2000) was lower than that of raw wastewater (418.1 mPET2000) and standard medium (497.3 mPET2000)-cultivated groups. Consequently, the method of culturing microalgae in modified wastewater and pyrolyzing algal residues has a potential to increase renewable energy production and reduce environmental impact.

230 Microalgae as an Alternative Feed Protein: Opportunities and Challenges

Abstract A major mission of the animal industry is to help protect global food security with little or no impacts on climate and environment. In fact, the global food security depends on a sustainable protein production and supply. Currently, there is a direct competition between feed and food protein need. As animal feeds use 70–80% of the produced soybean, alternative proteins are required to sustain the industry. This presentation will report research findings from three large consortium projects in exploring the dual application of microalgae as a new generation of feedstock for biofuel production and high-quality feed protein supply. A comprehensive review will be provided on effects of supplemental full- or de-fatted microalgal biomass in diets for broiler chickens, laying hens, pigs, and fish on their production performance, nutrient metabolism and molecular responses, and health values of their products. Discussions will be given on practical concerns over the production cost related to soybean meal, the production volume/scale for a constant supply, and the biosafety and acceptance as a regular ingredient. Future research will be proposed to synchronize the nutritional, health, and sustainability potential of microalgae as a viable feed protein source.

Incorporation of defatted microalgal biomass (Tetraselmis sp. CTP4) at the expense of soybean meal as a feed ingredient for juvenile gilthead seabream (Sparus aurata)

The forecasted growth of the aquaculture sector requires the use of novel and sustainable ingredients in aquaculture feeds. A study was undertaken to evaluate the effect of a 10% incorporation of defatted microalgal biomass (DMB) of Tetraselmis sp. CTP4, used at the expense of dehulled solvent-extracted soybean meal (SBM), on the growth performance, nutrient digestibility and physiological response to confinement stress in gilthead seabream juveniles. The trial comprised two dietary treatments: a control diet (CTRL) with relatively high levels of marine-derived proteins and 10% SBM; and a test diet (DMB10) with the incorporation of 10% DMB at the expense of SBM, while maintaining a fair constancy of all other ingredients. Triplicate groups of 30 fish, with a mean initial body weight of 6.0 ± 0.2 g were fed the experimental diets for 61 days. At the end of the trial, fish tripled their initial body weight, but the overall growth performance criteria (final body weight, daily growth index, feed conversion ratio and protein efficiency ratio), whole-body composition and nutrient retention were not significantly affected by the dietary treatments (p > 0.05). The DMB10 diet showed a significantly higher apparent digestibility coefficients (ADC) of dry matter, energy and phosphorus (p < 0.05). When measured as an isolated feed ingredient, the DMB had an ADC of protein, fat, energy and phosphorus of 87.9, 85.3, 75.5 and 41.4%, respectively. After an acute confinement stress test, fish fed with DMB10 diet displayed a significantly lower plasma cortisol response (120 ± 23 ng/mL) than those fed with the control diet (160 ± 33 ng/mL) (p < 0.05). Overall results showed that DMB, issued from biorefinery processes, could potentially spare the use of soybean meal in aquaculture feeds, contributing towards a reduction of the current protein deficit in the European market.

Occurrence forms of key ash-forming elements in defatted microalgal biomass

This study reports occurrence forms of key ash-forming elements in a defatted microalga, and for comparison, its corresponding raw microalga. Freeze-dried powders of a marine microalga (Nannochloropsis oceanica) were sieved to a size fraction of <75μm and used as raw microalga. The raw microalga was then extracted with hexane to remove crude lipids and prepare a defatted microalga. The raw and defatted microalgae were subjected to chemical fractionation analysis, i.e., sequential leaching in H2O, 1.0M ammonium acetate (NH4Ac), and 1.0M hydrochloric (HCl) acid. The results demonstrate that, whereas the contents of Fe and Al in the raw and defatted microalgae are extremely low, those of other ash-forming elements follow a sequence of Cl>K>P>Mg>Na>Ca. Chemical fractionation results suggest that virtually all of the Na, K, and Cl in the raw and defatted microalgae are water-soluble. While majority of P in the two fuels are water-soluble and acid-soluble, most of Mg and Ca are leached in water and NH4Ac solution. As determined via chemical fractionation analysis, lipid extraction leads to the content of water-soluble Ca in the defatted microalga being ∼69.6% higher than that in the raw microalga counterpart, which is accompanied by a reduction in the amount of Ca leached in NH4Ac solution. Similar trend is also observed for Mg, but to a lesser extent.

Characterisation of defatted Scenedesmus dimorphus algal biomass as animal feed

Defatted microalgal biomass (DAB) of a local Scenedesmus dimorphus strain was characterised as animal feed in an experimental Wistar rat model. The DAB contained 21.5 % protein, 28 % dietary fibre and 21 % ash on dry basis. The DAB was rich in calcium (1208 mg 100 g−1 biomass) followed by magnesium (400.6 mg 100 g−1) among the tested mineral elements. The essential amino acids (EAA) constituted 48 % (w/w) of proteins, and the EAA index was similar to casein and soybean. The protein was limiting in sulphur-containing amino acids cysteine and methionine. The algal biomass showed 5–6-fold higher water absorption capacity (3.44 ± 0.06 g g−1 biomass) compared with basal diet (0.67 ± 0.06 g g−1 biomass). The DAB was found to be safe in both short-term (14 days), single-dose feeding (20 % (w/w) feed) and long-term (90 days) repeated-dose feeding (at 5 and 10 % (w/w) feed). In the short-term feeding trial, faecal output and water intake increased by 2-fold during the initial 4 days, mainly attributed to higher ash and fibre content of biomass. The long-term repeated-dose feeding of DAB did not induce any physiological changes in rats such as feed intake, haematology profile, serum biochemical parameters, histopathology and relative organ weight. The feed conversion ratio and quotient of protein efficiency ratio in DAB-fed groups were similar to control. However, animals required a longer adaptation period to DAB-mixed feed, as indicated by slower body weight gain and feed intake. The study suggests that DAB can be used as animal feed up to 10 % (w/w) replacement levels.

Statistical optimization of thermal pretreatment conditions for enhanced biomethane production from defatted algal biomass.

The present study analyzes the effect of thermal pretreatment for enhancing the biomethane potential of defatted algal biomass of Scenedesmus dimorphus through statistically guided experimental design. To this end, defatted microalgal biomass at various concentrations (1, 3 and 5 g L(-1)) was pretreated at elevated temperatures (100, 120 and 150°C) for 20, 40 and 60 min. The solubilised TOC was favourably enhanced up to 71 mg L(-1) after pretreatment at a temperature of 150°C for reaction time of 60 min. The methane yield was substantially enhanced (up to 60%) and could be correlated with an increase in organic matter solubilisation and enhanced biodegradability via thermal pretreatment. The optimisation of the integrated thermal pretreatment-biomethanation process resulted in up to 1.6-fold increase in methane yield.

NONRUMINANT NUTRITION SYMPOSIUM: Potential of defatted microalgae from the biofuel industry as an ingredient to replace corn and soybean meal in swine and poultry diets12

While feeding food-producing animals with microalgae was investigated several decades ago, this research has been reactivated by the recent exploration of microalgae as the third generation of feedstocks for biofuel production. Because the resultant defatted biomass contains high levels of protein and other nutrients, it may replace a portion of corn and soybean meal in animal diets. Our laboratory has acquired 4 types of full-fat and defatted microalgal biomass from biofuel production research (Cellana, Kailua-Kona, HI) that contain 13.9 to 38.2% crude protein and 1.5 to 9.3% crude fat. This review summarizes the safety and efficacy of supplementing 2 types of the biomass at 7.5 to 15% in the diets of weanling pigs, broiler chicks, and laying hens. Based on their responses of growth performance, egg production and quality, plasma and tissue biochemical indicators, and/or fecal chemical composition, all 3 types of animals were able to tolerate the microalgal biomass incorporation into their diets at 7.5% (on as-fed basis). Holistic analysis is also provided to explore the global potential of using the defatted microalgal biomass as a new feed ingredient in offsetting the biofuel production cost, reducing the dependence on staple crops such as corn and soybeans, decreasing greenhouse gas production of animal agriculture, and developing health value-added animal products.

Dual potential of microalgae as a sustainable biofuel feedstock and animal feed.

The rise in global population has led to explorations of alternative sources of energy and food. Because corn and soybean are staple food crops for humans, their common use as the main source of dietary energy and protein for food-producing animals directly competes with their allocation for human consumption. Alternatively, de-fatted marine microalgal biomass generated from the potential biofuel production may be a viable replacement of corn and soybean meal due to their high levels of protein, relatively well-balanced amino acid profiles, and rich contents of minerals and vitamins, along with unique bioactive compounds. Although the full-fatted (intact) microalgae represent the main source of omega-3 (n-3) polyunsaturated fatty acids including docohexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the de-fatted microalgal biomass may still contain good amounts of these components for enriching DHA/EPA in eggs, meats, and milk. This review is written to highlight the necessity and potential of using the de-fatted microalgal biomass as a new generation of animal feed in helping address the global energy, food, and environmental issues. Nutritional feasibility and limitation of the biomass as the new feed ingredient for simple-stomached species are elaborated. Potential applications of the biomass for generating value-added animal products are also explored.