Use of microalgal biomass as functional ingredient for preparation of cereal based extrudates: impact of processing on amino acid concentrations and colour degradation kinetics

Abstract Suitability of developing Spirulina incorporated cereal based low cost nutritious extrudates was analysed against extrusion processing parameters. Most significant extrusion processing parameters considered for present study were feed moisture (20-25%), die temperature (100-120 °C) and screw speed (50-100 rpm). Different extrusion conditions were used to obtain most acceptable rice: Spirulina blend extrudates. In present study before extrusion processing different additives (citric acid and sodium bicarbonate) were added in rice: Spirulina blend and checked its effect on colour degradation kinetics at varied packaging and storage conditions. Higher screw speed (100 rpm) indicating less residence time of feed material inside the barrel resulted in higher colour retention of rice: Spirulina (97:03) blend extrudates. Kinetics for rice: Spirulina (97:03) blend extrudates indicates faster rate of colour degradation in terms of lightness (half-life of 4 days) when packed in metalized polyethylene at 50°C with 65% relative humidity. Increased concentration of Spirulina (1-3%) in raw formulations resulted in increase in concentration of all amino acids. Impact of extrusion processing has shown non-significant (p ≤ 0.05) effect on amino acid concentrations of rice: Spirulina blend extrudates. Also, all the spirulina added samples showed good consumer acceptability with the score of 6.7

Role of pH on antioxidants production by Spirulina (Arthrospira) platensis

Abstract Algae can tolerate a broad range of growing conditions but extreme conditions may lead to the generation of highly dangerous reactive oxygen species (ROS), which may cause the deterioration of cell metabolism and damage cellular components. The antioxidants produced by algae alleviate the harmful effects of ROS. While the enhancement of antioxidant production in blue green algae under stress has been reported, the antioxidant response to changes in pH levels requires further investigation. This study presents the effect of pH changes on the antioxidant activity and productivity of the blue green alga Spirulina (Arthrospira) platensis. The algal dry weight (DW) was greatly enhanced at pH 9.0. The highest content of chlorophyll a and carotenoids (10.6 and 2.4 mg/g DW, respectively) was recorded at pH 8.5. The highest phenolic content (12.1 mg gallic acid equivalent (GAE)/g DW) was recorded at pH 9.5. The maximum production of total phycobiliprotein (159 mg/g DW) was obtained at pH 9.0. The antioxidant activities of radical scavenging activity, reducing power and chelating activity were highest at pH 9.0 with an increase of 567, 250 and 206% compared to the positive control, respectively. Variation in the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) was also reported. While the high alkaline pH may favor the overproduction of antioxidants, normal cell metabolism and membrane function is unaffected, as shown by growth and chlorophyll content, which suggests that these conditions are suitable for further studies on the harvest of antioxidants from S. platensis.

Variation of Spirulina maxima biomass production in different depths of urea-used culture medium

Fewer studies have assessed the outdoor cultivation of Spirulina maxima compared with S. platensis, although the protein content of S. maxima is higher than S. platensis. Spirulina growth medium requires an increased amount of NaHCO3, Na2CO3, and NaNO3, which increases the production cost. Therefore, the current study used a low-cost but high-efficiency biomass production medium (Medium M-19) after testing 33 different media. The medium depth of 25 cm (group A) was sub-divided into A1 (50% cover with a black curtain (PolyMax, 12 oz ultra-blackout), A2 (25% cover), and A3 (no cover). Similarly the medium depths of 30 and 35 cm were categorized as groups B (B1, B2, and B3) and C (C1, C2, and C3), respectively, and the effects of depth and surface light availability on growth and biomass production were assessed. The highest biomass production was 2.05 g L-1 in group A2, which was significantly higher (p < 0.05) than that in all other groups and sub-groups. Spirulina maxima died in B1 and C1 on the fifth day of culture. The biochemical composition of the biomass obtained from A2 cultures, including protein, carbohydrate, lipid, moisture, and ash, was 56.59%, 14.42%, 0.94%, 5.03%, and 23.02%, respectively. Therefore, S. maxima could be grown outdoors with the highest efficiency in urea-enriched medium at a 25-cm medium depth with 25% surface cover or uncovered.

Salinidade da água e suplementação alimentar com microalga marinha no crescimento e masculinização de tilápia do Nilo / Water salinity and food supplementation with marine microalgae on growth and masculinization of nile Tilapia

O objetivo deste trabalho foi avaliar a influência da salinidade da água e suplementação alimentar com Spirulina platensis no crescimento e masculinização de Oreochromis niloticus, tilápia do Nilo. Na primeira fase, além da S. platensis, foi ofertada ração microparticulada (50% PB; 4500 Kcal/kg) contendo o andrógeno 17-α- metiltestosterona. Na segunda etapa, as tilápias foram cultivadas por mais 32 dias em água doce, alimentadas apenas com ração (38% PB; 1900 Kcal/kg). Os delineamentos foram divididos em três tratamentos com cinco repetições cada. Os animais (peso inicial: 0,01 ± 0,02 g, comprimento inicial: 1,0 ± 0,03 cm) ao final de 28 dias apresentaram crescimento médio em peso e crescimento total em comprimento de 1,64 ± 0,10 g e 4,84 ± 0,24 cm; 1,59 ± 0,18 g e 4,94 ± 0,12 cm e 1,58 ± 0,09 g e 4,84 ± 0,02 cm para as salinidades 0, 15 e 25 g.L-1, respectivamente. A masculinização mais satisfatória foi alcançada pelos peixes cultivados a 15 g.L-1, ao qual obtiveram 90% de machos. A análise de variância não evidenciou diferenças significativas (p>0,05) entre os tratamentos para o desenvolvimento em ambas as fases de cultivo e para a taxa de masculinização ao final do experimento. As salinidades testadas não interferiram no desempenho dos peixes, propondo que a microalga S. platensis pode ser utilizada com êxito como suplemento alimentar para tilápias do Nilo nas condições testadas.

The aim of this study was evaluate the influence of water salinity and diet supplemented with Spirulina platensis on growth and masculinization of Nile tilapia. In the first phase, in addition to S. platensis, was offered microparticulate diet (50% CP, 4500 Kcal/kg) containing 17-α-methyltestosterone androgen. In the second phase, the tilapias were cultivated for 32 days in fresh water, fed only with ration (38% CP, 1900 kcal/kg). The designs were divided into three treatments with five replicates each. The animals (initial weight: 0,01 ± 0,02 g, initial length: 1,0 ± 0,03 cm) after 28 days showed average weight growth and total length growth of 1,64 ± 0,10 g; 4,84 ± 0,24 cm, 1,59 ± 0,18 g; 4,94 ± 0,12 cm, 1,58 ± 0,09 g; 4,84 ± 0,02 cm, in salinities 0, 15 and 25 g.L-1, respectively. The indices of improvement sexual inducing were achieved by animals cultured at 15 g.L-1, which reached 90% of masculinization. Analysis of variance showed no significant differences (p>0,05) among treatments for development in cultivation phases both and the masculinization rate in the experiment final. The salinities tested did not interfere with the performance of fish, suggesting that the microalgae S. platensis can be successfully used as a food supplement for Nile tilapia in the tested conditions.