Ana Cláudia Margarites

Spirulina platensis biomass composition is influenced by the light availability and harvest phase in raceway ponds

ABSTRACT The behavior of cyanobacteria and its potential use for biofuel production in scale-up conditions is a topic of growing importance. The aim of our work is to study the effects of illumination, stirring, and different growth phases on the cultivation of the cyanobacteria Spirulina platensis in 10 L raceways. The cultivations were carried out in a greenhouse under measured, but not controlled, illumination and in agitated raceways with stirring speeds varying from 0.1 to 0.4 m s−1, using culture media with nutrient depletion. At the end of the stationary phase (SP) and decline of culture, the biomass was harvested and used to determine the chemical composition. The stirring rate and the growing phase influenced the carbohydrate concentration. In both phases of cultivation, compared to high-speed stirring, stirring at lower speeds produced fewer carbohydrates in the culture. Biomass grown until the end of the SP with a stirring speed of 0.35 m s−1 had a carbohydrate content of 72%, which is very high compared to that reported in the literature. GRAPHICAL ABSTRACT

Saccharification of Spirulina platensis biomass using free and immobilized amylolytic enzymes

We aimed to use physical methods of microalgal biomass rupture to study saccharification strategies using free and immobilized amylolytic enzymes. The biomass of Spirulina platensis, which consists of 50-60% carbohydrates, was exposed to physical cell rupture treatments, with better results obtained using freeze/thaw cycles following by gelatinization. In saccharification tests, it was possible to hydrolyze Spirulina biomass with hydrolysis efficiencies above 99% and 83%, respectively, using 1% (v/v) of free enzymes or 1% (m/v) of amylolytic enzymes immobilized together. The use of free and immobilized enzymes yielded high levels of conversion of polysaccharides to simple sugars in Spirulina biomass, showing that these processes are promising for the advancement of bioethanol production using microalgal biomass.

Ficocianina, tocoferol e ácido ascórbico na prevenção da oxidação lipídica em charque

This study aimed to evaluate the prevention of lipid oxidation in jerked beef through the use of natural antioxidant substances and the synthetic antioxidant BHT. It was used spare ribs from Holstein cattle to elaborate the jerked beef pieces. The treatments were: Control (no addition of antioxidant), Tocopherol (addition of 0,03 %), Phycocyanin (addition of 0,5 %), BHT (addition of 0,01 %), Tocopherol and Ascorbic acid (addition of 0,03 % of each one), and each treatment had five slabs of jerked beef. The percentages of antioxidants added were according to the lipid content of the raw material. After preparation, zero time, the slabs were stored for 60 days at room temperature, 25 °C. Representative samples were taken for the analysis of lipid oxidation by way of the peroxide value (PV) and 2-thiobarbituric acid reactive substances (TBARS). The antioxidants attenuated the lipid oxidation of jerked beef and, among the natural antioxidants which were tested, Phycocyanin showed the highest inhibition of peroxide formation. The antioxidant α-tocopherol presented a better efficiency when used synergistically with ascorbic acid. The TBARS results indicated that BHT showed the highest inhibition and, among the natural antioxidants tested, the mixture of ascorbic acid with tocopherol was more efficient. The use of natural antioxidants may become an alternative in delaying lipid oxidation in jerked beef and similar products.