Air Naturel GOTA Ultrasonic Air Humidifier User Manual download pdf (Page 291)

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

281

yeast extract, pH adjusted to 6.0, as proposed by Papanikolau et al. (2002), using raw glycerol as the main

carbon source. The suspension was incubated at 30°C in a rotary shaker with agitation rate at 180 rpm,

monitoring the cell concentration by counting in a Neubauer chamber.

The cultures were performed in 500 ml Erlenmeyer flasks containing 200 ml growth medium resulting of

add culture medium, yeast suspension and sterile distilled water. The culture medium was prepared in

concentrated form in order to result the following composition (g/L) proposed by Levinson et al. (2007): 40

raw glycerol, 1.7 KH

; 12 Na

HPO

; 1.25 MgSO

.7H

O; 0.25 yeast extract; 0.006 thiamine; 0.25

(NH

)

; pH adjusted to 6.0. The cultures was inoculated with yeast suspension previously prepared to

achieve 1x10

cells mL

-1

and maintained in an rotary shaker at 30 °C shaker with agitation rate at 180 rpm,

removing aliquots in the time intervals previously established, and samples were centrifuged at 1780 x g for

15 min.

Analysis determinations

The cell concentration was estimated by optical density at 680 nm using a methodology cited by Choi and

Park (2003). The biomass obtained was washed, centrifuged again at 1780 x g for 15 min and suspended in

appropriate volume to determine the cell concentration by optical density at 680 nm (spectrophotometer

Biospectro SP-220, China). The cell concentration was expressed as dry weight (g L

-1

), obtained from a

calibration curve previously determined for each microorganism. The pH was determined using a digital

potentiometer (Marte MB-10, Brazil) and the concentrations of citric acid and isocitric acid were determined

by enzymatic kits (R-Biopharm, Germany)

Statistical analysis

Experiments were performed in triplicate and the values were informed as means ± standard derivation. The

results were submitted to analysis of variance (ANOVA) and Tukey's test in order to verify significant

differences regarding the different in the concentration of citric and isocitric acid among yeasts tested, at

95% confidence level (p ≤ 0.05).

RESULTS AND DISCUSSION

The monitoring of cell concentration and pH during cultivation for the six yeasts strains can be viewed in

Figure 1a and 1b, respectively.

Figure 1: Cell concentration c (A) e pH (B) Medium of cultivation for yeast using glycerin as main carbon

source. Abbreviation: Y.L. yarrowia lipolytica; C.L. candida lipolytica, C.O. candida oleophila and C.C. c.

Regarding the cell concentration, it was found that maximum biomass produced by yeasts reached values of

5.16 ±0.21 g L

-1

, 7.80 ±0.11 g L

-1

, 7.33 ±0.21 g L

-1

, 7.16 ±0.16 g L

-1

,12.83

±0.61 g L

-1

e 8.51±0.41 gL

-1

for Y.

lipolytica Y-1094, Y. lipolytica YB-423, Y. lipolytica Y-11853, C. lipolytica Y-1095, C. oleophila Y-2317,

C. cylindracea Y-17506, respectively, at 216 h cultivation. In relation to the pH, more pronounced variation

was observed for the yeasts Y. lipolytica Y-1094, Y. lipolytica YB-423, Y. lipolytica Y-11853 and C.

lipolytica Y-1095, 3.08, 3.27, 3.65 e 3.34, respectively.

0 24 48 72 96 120 144 168 192 216 240

Time (hour)

2,5

3,0

3,5

4,0

4,5

5,0

5,5

6,0

6,5

Y,L yb-423

Y.L.y-1094

Y.L y-11853

C.L y-1095

C.O.y-2317

C.C.y-17506

( B )

0 24 48 72 96 120 144 168 192 216 240

Time (hour)

Cell concentration (g/L)

Y.L yb-423

Y.L y-1094

Y.L y-11853

C.L y-1095

C.O y-2317

C.C y-17506

( A )

1 2 ... 286 287 288 289 290 291 292 293 294 295 296 ... 327 328

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