Air Naturel GOTA Ultrasonic Air Humidifier User Manual download pdf (Page 209)

IV Congreso Internacional de Ciencia y Tecnología de Alimentos - Córdoba, Argentina 14 a 16 de Noviembre de 2012

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usual composition has a protein content of 53%, carbohydrates content of 23%, 9% lipids content and 5%

mineral content (Henrikson 1994). Some species of Chlorella have the capacity of growing in

photoautotrophic environments, as well as heterotrophic condition. A specie capable of such behavior is

Chlorella protothecoides (Wu et al. 1994).

Chlorella minutissima is a green algae, microscopic and usually found in fresh water systems. This species is

characterized as having a rigid cellular wall, as well as a large amount of chlorophyll. C. minutissima

chlorophyll content is larger than other superior algae (Morais 2006). Economical interest in its culture has

been growing due to a series of characteristics. Such characteristics are, relatively easy culture, high protein

content, capable of achieving up to 65% of its dry weight, varying according to the culture conditions

(Venkataraman and Becker 1985).

Microalgae autotrophic culture is conducted by utilizing carbon dioxide as carbon source, and sun light as

energy provider. The energy is necessary to establish a proton gradient capable of turning inorganic into

organic carbon trough a series of reactions. However, some microalgae species also have the ability of

growing under mixotrophic conditions. In this system, two carbon sources are utilized simultaneously. Both

carbon dioxide and an organic carbon source are utilized, as well as sun light as a proton gradient generator

(Chojnacka and Marquez-Rocha 2004).

In the microalgae heterotrophic cultures, such as those with organic carbon sources, carbohydrates are the

most utilized group (Cid et al. 1992), specially glucose (Miao and Wu 2006, Xu et al. 2006, Liang et al.

2009, Heredia-Arroyo et al. 2010, Shen et al. 2010, O’Grady and Morgan 2011). However, other organic

carbon sources may be utilized, such as glycerol (Liang et al. 2009, O’Grady and Morgan 2011), acetate

(Liang et al. 2009, Heredia-Arroyo et al. 2010), among others. When compared with the autotrophic culture,

this sort of culture provides several advantages, such as, the elimination of light requirement, a simpler

culture control and, biomass downstream coast reduction, due to the larger cellular density obtained (Chen

and Johns 1991).

D-glucose is a carbohydrate (molecule which posses a carbon atom together with hydrogen and oxygen

atoms, in the same proportion as they occur in water molecules) and it is the most abundant organic

compound. This molecule is characterized as a monosaccharide. Glucose is also considered to be an polyol

and an aldehyde. When D-glucose is represented in its open chain or vertical form, know as its alicyclic

structure, it has an aldehyde group in one extremity (carbon atom 1), and a primary hydroxyl group in the

other extremity (carbon atom 6). Secondary hydroxyl groups are connected to the inner carbon atoms, they

are 2, 3, 4 and 5, all of which have four different substituents, making them all chiral (Damodaran et al.

2010).

This work objective was to evaluate glucose utilization as a carbon source in heterotrofic culture of the

microalgae Chlorella minutissima in different culture media for biomass production.

MATERIAL AND METHODS

Microorganism and culture media

In this study the microalga Chlorella minutissima was utilized. This species belongs to the collection of the

Laboratory of Biochemical Engineering from the Federal University of Rio Grande – FURG (Rio Grande,

Brazil). The microalga was cultivated in BG11 medium (Rippka et al. 1979) containing (g.L

-1

): NaNO

: 1.50;

HPO

.3H

O: 0.04; MgSO

.7H

O: 0.075; CaCl

.2H

O: 0.036; Ferric ammonium citrate: 0.006; Disodic

EDTA: 0.001; Na

: 0.02; Citric Acid: 0.006; H

: 2.86; MnCl

.4H

O: 1.81; ZnSO

.7H

O: 0.222;

MoO

.2H

O: 0.39; CuSO

.5H

O: 0.079; Co(NO

)

.6H

O: 0.0494; and in Basal medium (Wu et al. 1992)

containing (g.L

-1

): KH

: 0.7; K

HPO

: 0.3; MgSO

·7H

O: 0.3; FeSO

·7H

O: 0.003; glycine: 0.1; B1

vitamin: 0.00001 and of 1 mL.L

-1

A5 mineral solution.

Culture conditions

Heterotrophic cultures of Chlorella minutissima microalga were realized. The microalga was cultivated in

BG11 and Basal media complemented with 0, 5 and 10 g.L

-1

of glucose in a feed batch process. The glucose

addition to the cultures was realized daily with one tenth of its final glucose concentration being added (5

and 10 g.L

-1

). The experiments, as well as the glucose addition, lasted for 10 days. The cultures were carried

in orbital shakers (INNOVA

44) at 150 RPM and 30°C. The utilized reactor was a closed bioreactor (2L

erlenmeyer) with 1.6L of solution. The initial cellular concentration was 0.15 g.L

-1

. Each glucose final

concentration generated an experiment; these were realized in duplicates, totaling 12 essays. At the end of

each experiment the solution was centrifuged. The precipitate was then dried at 40°C for 60h and ground.

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