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Production of Rhodotorula glutinis: a yeast that secretes α-L-arabinofuranosidase Claudio Martínez Cecilia Gertosio Angelica Labbe Rafael Pérez Maria Angélica Ganga* *Corresponding author Financial support: This investigation was financed by the grant Fondef D98I1037, Keywords: α-L-arabinofuranosidase yeast, enzymes, wine.
The aroma of wine is one of the most important organoleptic characteristics in the evaluation of the quality of this product. In the grape or must juice there are a great number of compounds of potential interest participating in the aromatic fraction of wines. These compounds, known as glycosides, consist of a disaccharide (glucose plus another sugar) joined to a volatile compound (Gunata et al. 1985) and it is because of this structure that the latter compound does not participate in the composition of the aroma. However, Gunata et al. (1988) have described that these volatile compounds could be liberated by enzymatic or chemical hydrolysis during fermentation by the initial action of an enzyme that hydrolyzes the sugar-glucose bond, and through the action of a second enzyme, hydrolyze the glucose-volatile compound bond. The same authors have described that the sugar-glucose union is formed mainly by a molecule of α-L-arabinofuranoside, which therefore makes it interesting to use an enzyme that hydrolyses this bond to initiate the process of liberating the volatile compound.. In light of the potential use that an L-arabinofuranosidase (Abf) activity would have in the enological industry, in this work we studied the culture conditions of Rhodotorula glutinis, a yeast that has been shown to produce Abf activity and which is naturally present in fermentative processes. For this research R. glutinis strain L-1816 isolated from Chilean grapes of the Cabernet Sauvignon variety was used. The basal growth medium used was similar to that described by Uesaka et al. (1978) with the following modifications: 2% (w/v) glucose, 0.5% (w/v) yeast extract and a salts solution composed of 0.3% (w/v) (NH4)2SO4, 0.1% (w/v) KH2PO4 and 0.05% (w/v) MgSO4 x 7H2O. To evaluate the effect of these compounds on yeast growth, we first studied how the presence or absence of peptone can influence the rate growth of R. glutinis strain L-1816. Using the basal medium previously described, it was determined that the use of peptone at 0.5% (w/v) did not affect growth rate, suggesting that the nitrogen supplied by the peptone may be covered by nitrogenated salts found in the basal medium. Subsequently, how the composition and types of salt of the culture media affect yeast growth were determined. The composition of salts I corresponded to that described previously while salts II (0.3% (w/v) (NH4)2SO4, 0.1% (w/v) KH2PO4, 0.05% (w/v) MgSO4 x 7H2O and 0.005% (w/v) FeSO4 x 7H2O), III (0.3% (w/v) (NH4)2SO4, 0.1% (w/v) KH2PO4, 0.05% (w/v) MgSO4 x 7H2O and 0.001% (w/v) MnCl2 x 4H2O) and IV (0.3% (w/v) (NH4)2SO4, 0.1% (w/v) KH2PO4, 0.05% (w/v) MgSO4 x 7H2O, 0.005% (w/v) FeSO4 x 7H2O and 0.001% (w/v) MnCl2 x 4H2O). Results showed that the addition of Fe and Mn salts had a negative effect on yeast growth. As a way of using alternative carbon sources, beet molasses (IndustriaAzucareraNacional S.A (Iansa)-Chile) and beet cosette (Iansa-Chile) were used independently in the culture medium, evaluating their effect on the rate growth of R. glutinis L-1816 as well as in the production of Abf. To the basal medium previously described glucose, beet cosette and beet molasses were added individually at a concentration of 2%, culture of the yeast was at Considering these previous findings, the yeast was finally grown in a continuous fermentation system for 80 hrs to produce Abf. Two flow velocities were assayed: 0.064 and 0.178 h-1, with an average specific activity for the enzyme of 82.4 U/mg of protein was obtained.
GUNATA, Ziya; BITTEUR, Sylvaine; BRILLOUET, Jean-Marc; BAYONOVE, Claude and CORDONNIER, Robert.Sequential enzymic hydrolysis of potentially aromatic glycosides from grape. Carbohydrates Research, December 1988, vol. 184, p. 139-149. [CrossRef] UESAKA, E.; SATO, M.; RAIJU, M. and KAJI, A. α-L-Arabinofuranosidase from Rhodotorulaflava. The Journal of Bacteriology, March 1978, vol. 133, no. 3, p. 1073-1077. |
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