Fatty Acid Biosynthesis from Chlorella in Autotrophic and Mixotrophic Cultivation

Abstract Microalgae are photosynthetic microorganisms whose composition and biomass production can be influenced by manipulating the cultivation conditions employed. However, few studies have evaluated the effects of various cultivation conditions in autotrophic and mixotrophic conditions. The present work aimed to evaluate the effects of cultivation conditions on the cell growth and biosynthesis of fatty acids (FAs) by microalgae of the genus Chlorella in autotrophic and mixotrophic cultivation. Evaluation of the effects of the conditions was performed using an experimental design methodology. The highest values of maximum biomass concentration (Xmax) and maximum biomass productivity (Pmax) were obtained in autotrophic cultures. Palmitic acid was the FA obtained at the highest concentration in both cultivation modes. The concentrations of polyunsaturated FAs (PUFAs) ranged from 12.2 to 41.2% in autotrophic cultures and from 11 to 34.3% in the mixotrophic cultures. The variables photoperiod and sodium bicarbonate concentration showed the greatest influence on the Xmax, Pmax, and PUFA concentration in autotrophic and mixotrophic cultivations, respectively. This study verified that the selection of conditions and mode of cultivation contribute to the production of microalgal biomass and FA biosynthesis.

Transformation of Brewery Subproducts into Valuable Biomass Using Mixotrophic Culture of Chlorella pyrenoidosa and Associated Bacteria

Abstract To develop a biorefinery concept applied in the brewery industry, Chlorella pyrenoidosa and a consortium of associated bacteria were cultivated mixotrophically in a continuous photobioreactor using brewery low-value subproducts as an integrative process. Beer production residues were biochemically characterized to assess the most promising options to be used as a nutrient source for microalgal cultivation. Due to its physical and chemical properties, pre-treated weak wort was used to prepare an organic complex culture medium for microalgal biotransformation. Filtration and nitrogen supplementation were necessary to improve nutrient removal and biomass productivity. Maximal removal of nitrate and phosphate obtained were 90% and 100% respectively. Depending on operation conditions, total carbohydrates depuration ranged from 50 - 80%. The initial concentration of total carbohydrates of the weak wort must be adjusted to 2 - 4g/L to maintain a stable equilibrium between microalgal and bacterial growth. The biochemical composition of produced biomass varied depending on the cultivation conditions as well as on its final use. Upon continuous mixotrophic conditions evaluated in this study, C. pyrenoidosa was composed mainly of carbohydrates and protein.

Effect of Brachionus rubens on the growth characteristics of various species of microalgae

Background: Cultivation of algae for conversion to biofuels has gained global interest. Outdoor raceway cultivation is preferred because of its lower capital and operating costs. A major disadvantage of outdoor cultivation is susceptibility of algal crops to attack by predatory rotifers. In order to quantify the impact of rotifer attack on different species of algae, we evaluated the growth of eleven microalgal species over a 21-d period after being infected by the predatory rotifer Brachionus rubens. Results: Of the eleven species, Chlorella sorokiniana was the most susceptible with rapid decline in algal growth concomitant with increase in rotifer population growth (3.82/d). In contrast, Synechococcus elongatus andScenedesmus dimorphus were both resistant to the rotifer and suppressed rotifer growth (-0.06/d). An index of algal species susceptibility to be consumed by the rotifer was generated with C. sorokiniana as the baseline (index = 1.000) indicating most susceptible among species tested. Other species' susceptibilities are indicated in parenthesis as follows: Monoraphidium spp. (0.997), Chlamydomonas globosa (0.827), Botryococcus braunii(0.740), Chlorella minutissima (0.570), Chlamydomonas augustae (0.530), Chlamydomonas yellowstonensis (0.500), Scenedesmus bijuga (0.420), and Haematococcus pluvialis (0.360). Two species, namely, S. dimorphus andS. elongatus were unique in that they exhibited an ability to suppress the growth of the rotifer as indicated by the decline in rotifer populations in their presence. Conclusions: Variations in susceptibility of algal species to rotifer predation could be a result of their individual morphology, cell walls structure, or the biochemical composition of individual species.

Teores de proteínas e lipídeos de Chlorella sp. cultivada em concentrado de dessalinização residual / Protein and lipid contents from Chlorella sp. Cultivated in residual concentrated desalination

A dessalinização é um método de obtenção de água potável limitado pelos problemas ambientais, causados pelo resíduo gerado em seu processo. O objetivo deste estudo foi avaliar o cultivo de Chlorella sp., em meio de cultura a base de concentrado de dessalinização, e determinar os teores de proteínas e lipídeos ao longo dos ciclos de cultivo. Os cultivos foram desenvolvidos em fotobiorreatores cônicos invertidos (4L) e mantidos durante 28 dias resultando em quatro ciclos de cultivo. Para cada ciclo de cultivo, os valores de biomassa (peso seco, g L-1) resultaram em 1º ciclo, 1,55; 2º ciclo, 0,96; 3º ciclo, 0,62, e 4º ciclo em 0,42. Os teores de proteínas e lipídeos variaram entre 45,2 a 48,8% e 8,5 a 11,4%, respectivamente. O primeiro ciclo de cultivo apresentou a maior produtividade em biomassa (PB = 200 mg L-1 dia-1) e produtividade lipídica (PL = 19,6 mg L-1 dia-1), bem como o maior teor de proteínas (48,8%). O maior teor de lipídeos (11,4%) foi obtido no segundo ciclo de cultivo. Foi observado, nos quatro ciclos de cultivo, que a produtividade em biomassa está diretamente correlacionada com a produtividade lipídica, indicando que quanto maior a PB maior será a PL. Os resultados da cultura de Chlorella sp. demonstraram que é possível utilizar o concentrado de dessalinização residual como meio de cultura alternativo e obter biomassa ao longo de quatro ciclos de cultivo, sem comprometer os teores de proteínas e lipídeos na célula microalgal.

Desalination process is a method of obtaining potable drinking water which is limited by environmental problems caused by the waste generated in the process. The aim of this study was to evaluate the cultivation of Chlorella sp. in a culture medium based on residual concentrated desalination and determines the protein and lipid contents along the cultivation cycles. The cultures were developed in a reverse conical photobioreactors (4L) during 28 days resulting in four cultivation cycles. For each cultivation cycle, the value of biomass (dry weight g L-1) resulted: 1st cycle, 1.55 g; 2nd cycle, 0.96; 3rd cycle, 0.62 and 4th cycle, 0.42. The protein and lipid levels ranged from 45.2 to 48.8% and 8.5 to 11.4%, respectively. The first cultivation cycle showed the highest biomass productivity (PB = 200 mg L-1 dia-1) and lipid productivity (PL = 19.6 mg L-1 dia-1), as well as the highest protein content (48.8%). The highest lipid content (11.4%) was observed on second cultivation cycle. It was observed during the four cultivation cycles that the biomass productivity is directly correlated to lipid productivity, indicating that higher PB higher will be PL. The results from this study showed that it is possible to growth Chlorella sp. in a culture medium based on residual concentrated desalination for biomass production along the four cultivation cycles and also, without compromise the protein and lipid contents into the microalgal cell.

Nutrient enrichment and its effects on growth and metabolism of chlorella vulgaris and phormidium laminosum

In this study, the dry weight and chlorophyll a content of Chlorella vulgaris and Phormidium laminosum progressively increased with elevation of phosphate and nitrate doses supplemented to the culture media. The accumulation of total carbohydrates in both organisms were suppressed at all phosphate levels, but in Phormidium, it was stimulated under nitrate treatments. Both salts singly caused a drop in nitrate uptake which was associated by decrease in protein and total nitrogen contents. All phosphate levels stimulated the phosphorus absorption from the media and the phosphorus contents of both organisms while, the nitrate effect showed no constant trend. Irrespective of some fluctuations there was a clear trend for the mixture effects which are expressed by increase in dry weight, chlorophyll a, total carbohydrate accumulation, nitrate uptake, phosphorus uptake and contents in both algae. Total nitrogen and protein accumulation were adversely affected in most mixture treatments. Lowering the concentration of either phosphate or nitrate in both algal cultures below control levels suppressed the growth and inactivate the physiological processes. The N/P uptake ratios were generally decreased following limitation and/or enrichment with nitrate and phosphate

Estudo comparativo do crescimento de chlorella em condiçöes autotróficas e mixotróficas / Growth behavior of chlorella species in autotrophic and mixotrophic environments-a comparative study

resumo:Três meios de cultivo(o de Allen, 1952 modificado, o de Sorokin & Krauss, 1958 e o de Pratt, 1963) foram utilizados nos crescimentos autotróficos.Os cultivos foram conduzidos em agitadores recíprocos a 120 OPM, a 30 +/- 1ºC por 120 hs., sob iluminaçäo contínua, sendo o CO2 o disponível no ar atmosférico.O melhor crescimento foi observado para C.vulgaris em meio de Allen modificado, tendo sido de 0, 53 g/l (massa seca) a biomassa final.Esta microalga, juntamente com C.vulgaris var.viridis.C.ellipsoidea mostrou um crescimento insignificante.As fontes de nitrogênio proporcionaram crescimentos semelhantes em autotrofia.Variaçöes morfológicas praticamente näo foram observadas nos cultivos autotróficos, para cada espécie individualmente.Entre as espécies houve variaçöes de 2, 66 µm +/- 0, 1(C.homosfera) a 5, 7 µm +/- 0, 2 (C.vulgaris).Com relaçäo ao crescimento na presença de fontes de carbono orgânicas, C.vulgaris, C.homosfera e C.ellipsoidea apresentaram boas características para cultivos mixotróficos, sendo que todas responderam com aumento de biomassa a glicose, galactose, frutose e sacarose.C.vulgaris mostrou também a capacidade de assimilar o ácido acético, característica importante em termos industriais.Já C.vulgaris var.viridis näo respondeu a nenhuma fonte.C.homosfera foi a cepa que apresentou maiores variaçöes morfológicas, especialmente em crescimento mixotrófico.Entretanto, células gigantes näo foram formadas -