Aphanothece Microscopica Research Articles

Effect of light cycles (night/day) on CO 2 fixation and biomass production by microalgae in photobioreactors

The objective of this study was to evaluate the effect of the photoperiod on the biomass production and carbon dioxide fixation rates using a photosynthetic culture of the cyanobacterium Aphanothece microscopica Nägeli in bubble column photobioreactors. The cultures were carried out at temperatures of 35 °C, air enriched with carbon dioxide at concentrations of 15% and photon flux density of 150 μmol m −2 s −1. The light cycles evaluated were 0:24, 2:22, 4:20, 6:18, 8:16, 10:14, 12:12, 14:10, 16:8, 18:6, 20:4, 22:2 and 24:0 (night:day), respectively. The results obtained indicated that the duration of the light periods was a determinant factor in the performance of the photobioreactors. A linear reduction in biomass production and carbon dioxide fixation with reductions in the duration of the light period was evident, with the exception of the 12:12 (night:day) cycles. Reductions of up to 99.69% in the carbon-fixation rates as compared with cultures under continuous illumination were obtained.

Biomass production and carbon dioxide fixation by Aphanothece microscopica Nägeli in a bubble column photobioreactor

The objective of the present study was to evaluate the growth kinetics of Aphanothece microscopica Nägeli under different conditions of temperature, light intensity and CO 2 concentration. The growth kinetics of the microorganism and carbon biofixation were evaluated using a central composite design, considering five different temperature levels (21.5, 25, 30, 35 and 38.5 °C), light intensities (0.96, 3, 6, 9 and 11 klux) and carbon dioxide concentrations (3, 15, 25, 50 and 62%). The results obtained showed the effects of temperature, light intensity and CO 2 concentration ( p < 0.05) on the photosynthetic metabolism of the microorganism. Response surface methodology was adequate for process optimisation, providing a carbon fixation rate to the order of 109.2 mg L −1 h −1 under conditions of 11 klux, 35 °C and 15% carbon dioxide, representing an increase of 58.1% as compared to the conditions tested initially.

Rates of CO 2 removal by Aphanothece microscopica Nägeli in tubular photobioreactors

The integral method for the analysis of kinetic data was used to describe the removal of carbon dioxide dissolved in the aqueous phase of a tubular photobioreactor by Aphanothece microscopica Nägeli. The effects of the carbon dioxide concentration (3, 15, 25, 50 and 62%), light intensity (960, 3000, 6000, 9000 and 11,000 lux) and temperature (21.5, 25, 30, 35 and 38.5 °C) were considered using a central composite design, aiming to determine the most efficient system conditions. Response surface methodology showed the importance of the operational parameters of the photobioreactor on the kinetics of carbon dioxide removal, a good fit of the first order kinetic model to the experimental data being obtained.

Production and biochemical profile of the microalgae Aphanothece microscopica Nägeli submitted to different drying conditions

The production and biochemical profile, consisting of the protein, carbohydrate, lipid and fatty acid fractions of the microalgae Aphanothece microscopica Nägeli, cultivated in parboiled rice effluent, were studied with the objective of evaluating its potential as a source of metabolites of commercial interest. The biomass was produced in a batch cylindrical bioreactor operating isothermally at 30 °C, with the pH adjusted and maintained at 8.0, an inoculum concentration of 100 mg/L and C/N ratio of 50. The biomass was separated by centrifugation and dried in a batch tray dryer with parallel air flow (1.5 m/s) at temperatures of 40, 50 and 60 °C and tray thicknesses of 5 and 7 mm, followed by a biochemical evaluation. The results obtained showed that the parboiled rice effluent was a culture medium with potential for the production of single cell protein, and that the biomass produced represented an important source of protein, carbohydrate and lipids. The drying conditions were shown to significantly affect ( α = 0.05) the macronutrient composition of the biomass with respect to the protein, carbohydrate and lipid contents. The lipid profile showed a predominance of polyunsaturated fatty acids, especially that of gamma linolenic acid, but the drying conditions did not influence the polyunsaturated/saturated ratio of the biomass.

The kinetics of the removal of nitrogen and organic matter from parboiled rice effluent by cyanobacteria in a stirred batch reactor

The aim of this research was to evaluate the kinetics of the removal of nitrogen and organic matter from parboiled rice effluent by the cyanobacteria Aphanothece microscopica Nägeli. From the results obtained, it was verified that maximum efficiency for the removal of organic matter expressed as COD and total nitrogen (N-TKN) occurred after 15 h of cultivation, being 83.44% and 72.74, respectively. The scale-up process indicated that the volume of the estimated reactor would be 100.2 m 3, containing parboiled rice effluent and biomass.

Characteristics of thin-layer drying of the cyanobacterium Aphanothece microscopica Nägeli

This study was undertaken to investigate the dehydration characteristics of the cyanobacterium Aphanothece microscopica Nägeli in a convective hot-air dryer. The dehydration characteristics of the biomass were examined at air temperatures of 40, 50 and 60 °C and sample thicknesses of 3, 5 and 7 mm. During the dehydration experiments, air velocity was held stable at 1.5 m/s (parallel flow). The effects of air temperature and sample thickness on the dehydration characteristics and quality parameters (instrumental colour and chlorophyll a) of the dehydrated biomass were determined. The transport of water during dehydration was described by Fick's equation and effective diffusivity was between 8.1 × 10 −8 and 18.8 × 10 −8 m 2 s −1 . The experimental dehydration data on biomass obtained were fitted to the Henderson and Pabis model, and the drying rate constant was between 0.005 and 0.024 min −1. The response surface methodology was very efficient in determining product quality, showing the strong effect of temperature on instrumental colour and chlorophyll a content. The thicknesses evaluated showed a less significant effect on the final quality.

Caracterização da fração protéica da cianobactéria Aphanothece Microscopica Nägeli cultivada no efluente da parboilização do arroz

O objetivo do presente trabalho foi avaliar a fracao proteica da cianobacteria Aphanothece microscopica Nageli cultivada no efluente da parboilizacao do arroz quando submetida a diferentes condicoes de secagem. A producao da biomassa foi realizada a partir da agua residuaria do processo de parboilizacao do arroz em bioreatores de coluna de bolhas. A biomassa foi separada do efluente por centrifugacao e desidratada em secador descontinuo de bandejas nas condicoes de 40, 50 e 60oC e espessuras de bandejas de 5 e 7 mm. O comportamento eletroforetico das proteinas da biomassa foi analisado por eletroforese em gel de poliacrilamamida na presenca de dodecil sulfato de sodio (SDS-PAGE) e apresentou bandas com peso molecular de 15 kDa a 62,5 kDa. O perfil aminoacidico mostrou teores superiores aos recomendados pelo padrao FAO, com excecao dos aminoacidos lisina e dos sulfurados (MET+CYS). A caracterizacao funcional, expressa em termos de solubilidade e capacidade emulsificante, demonstrou a influencia da condicao de secagem na funcionalidade proteica da biomassa.