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Note on D-xylonate Utilization by Ascomycetous and Basidiomycetous Yeasts
System. App!. Microbio!. 13, 192-193 (1990) © Gustav Fischer Verlag, StuttgartlNew York
Note on D-xylonate Utilization by Ascomycetous and Basidiomycetous Yeasts ]. P. VAN DER WALT
and
ROSEMARIE L. STEYN
Division of Food Science and Technology, Council for Scientific and Industrial Research, Pretoria 0001, South Africa
Received November 2, 1989
Summary Fourteen strains representing 14 yeast species capable of utilizing D-xylose were examined for their ability to utilize D-xylonate. Of these 14 strains, six (three of ascomycetous and three of basidiomycetous affinity) were found to utilize D-xylonate. The possibility that certain D-xylose-utilizing yeasts may metabolize this sugar by a novel oxidative route which implicates the formation of D-xylonate as intermediate, is raised.
Key words: D-xylonic acid - D-xylose metabolism - Yeasts
Introduction While the metabolic route mediating the direct oxidation of D-xylose to xylono-y-Iactone is known to exist in bacteria and has partly been elucidated in Gluconobacter oxidans (Buchert and Viikari, 1988), very little appears to be known of the possible occurrence of this pathway in yeasts. Suzuki and Onishi (1967) have, however, reported to accumulation of D-xylonic acid and xylitol by a strain of Pichia quercuum Phaff et Knapp when cultured in a mixture of D-glucose and D-xylose (ratio 10: 0.1). Although Suzuki and Onishi (1967) did not clarify the mechanism, it is apparent that this accumulation of Dxylonic acid by P. quercuum must be attributed to absence or low efficiency of the systems mediating its complete oxidation. The possibility that other yeasts might metabolize D-xylose via an oxidative pathway involving the formation of D-xylonate, nevertheless, exists. Since the verification of such a route relies on the availability of strains utilizing D-xylonate, this character was examined in a limited number of yeast strains capable of utilizing Dxylose.
Material and Methods The strains studied (listed under Results) are held by the Yeast Division of the Centraalbureau voor Schimmelcultures in Delft (The Netherlands). For further details, reference is made to the 1987 CBS List of Cultures.
The utilization of D-xylonate as sole source of carbon by these strains was examined by the standard method described by Van der Walt and Yarrow (1984), using 6.8 g anhydrous potassium D-xylonate per 6.7 g Difco Yeast Nitrogen Base. Tubes were incubated at 25°C on a Tissue Culture Roller Drum (New Brunswick) rotating at 40 rph. The strains of Bullera alba and Bullera singularis were grown at 20°C because of their lower optimal growth temperature. Results were scored after 3, 7 and 14 days. When maximum growth occurred after 7 days, utilization was rated as delayed (D). The results are given in Table 1.
Results Results are given in Table
1.
Discussion The results in Table 1 is the first report confirming Dxylonate utilization by strains of divergent yeast species utilizing D-xylose. Of the 14 species tested, six utilized Dxylonate. These comprise the ascomycetous taxa Candida acuta Goto, Candida edax Van der Walt et Nel, Zygozyma arxii Van der Walt et a1. as well as the basidiomycetous taxa Bullera alb Hanna (Derx), Bullera singularis (Phaff et Do Carmo-Sousa), Rodrigues de Miranda and Cryptococcus amylolentus (Van der Walt et
D-xylonate Utilization by Yeasts
al.l Golubev. While these strains could conveniently serve for the elucidation of the possibly novel, oxidative pathway from D-xylose in yeasts, the utilization of D-xylonate
Table 1. Utilization of D-xylonate by D-xylose-utilizing yeasts Strains
D-Xylose 1
Utilization of: XylitoP D-Xylonate
Ambrosiozyma monospora CBS 2554
+
+
Bullera alba CBS 501 singularis CBS 501
+ +
+
D D
Candida acuta CBS 7053 boidinii CBS 2428 edax CBS 5657 homilentoma CBS 6312 utilis CBS 9950
+ + + + +
+ + + + +
+
Cryptococcus amylolentus CBS 6039
+
+
+
Debaryomyces hansenii CBS 767
+
+
Geotrichum eriense CBS 5974
+
+
Hormoascus ambrosiae CBS 6003
+
+
Pichia stipitis CBS 5773
+
+
Zygozyma arxii CBS 7333
+
1
Data from Barnett et al. (1983)
193
itself must, at present, only be considered as presumptive of such route; the ability to utilize D-xylonate does not of necessity imply the presence of the specific dehydrogenase mediating the conversion of D-xylose to either xylono-ylactone or xylono-6-lactone. The failure of the D-xyloseutilizing strains to metabolize D-xylonate could be due to the absence of systems mediating either its transport into the cell, or further oxidation via as yet undetermined intermediates. Given the distinctive route for the metabolism of D-xylonate, which precludes this compound entering the pentose cycle as D-xylulose-S-phosphate, the utilization of D-xylonate could carry sufficient weight as a physiological differentia for discriminating yeast species - notably among D-xylose utilizing taxa. Acknowledgement. The authors thank Dr. R. M. Horak for the gift of potassium D-xylonate.
+
References Barnett, j. A., Payne, R. W., Yarrow, D.: Yeasts: characteristics
+
and identification. Cambridge, Cambridge University Press 1983 Buchert, j., Viikari, L.: Oxidative D-xylose metabolism of Gluconobacter oxidans. App!. Microbio!. Biotechno!' 29, 375-379 (1988) Suzuki, T., Onishi, H.: The production of xylitol and D-xylonic acid by yeasts. Agr. Bio!. Chern. Oapan) 31, 1233-1236 (1967) Van der Walt, J. P., Yarrow, D.: Methods for isolation, maintenance, classification and identification of yeasts, pp. 45-104. In: The Yeasts, a taxonomic study (N. j. W. Kreger-van Rij, ed.), 3rd ed. Amsterdam, Elsevier, Science Pub!. BV 1984
Prof. Dr. j. P. Van der Walt, Department of Microbiology and Biochemistry, University of the Orange Free State, P.O. Pox 339, Bloemfontein 9300, South Africa
14 System. Appl. Microbiol. Vol. 13/2
Note on D-xylonate Utilization by Ascomycetous and Basidiomycetous Yeasts ]. P. VAN DER WALT
and
ROSEMARIE L. STEYN
Division of Food Science and Technology, Council for Scientific and Industrial Research, Pretoria 0001, South Africa
Received November 2, 1989
Summary Fourteen strains representing 14 yeast species capable of utilizing D-xylose were examined for their ability to utilize D-xylonate. Of these 14 strains, six (three of ascomycetous and three of basidiomycetous affinity) were found to utilize D-xylonate. The possibility that certain D-xylose-utilizing yeasts may metabolize this sugar by a novel oxidative route which implicates the formation of D-xylonate as intermediate, is raised.
Key words: D-xylonic acid - D-xylose metabolism - Yeasts
Introduction While the metabolic route mediating the direct oxidation of D-xylose to xylono-y-Iactone is known to exist in bacteria and has partly been elucidated in Gluconobacter oxidans (Buchert and Viikari, 1988), very little appears to be known of the possible occurrence of this pathway in yeasts. Suzuki and Onishi (1967) have, however, reported to accumulation of D-xylonic acid and xylitol by a strain of Pichia quercuum Phaff et Knapp when cultured in a mixture of D-glucose and D-xylose (ratio 10: 0.1). Although Suzuki and Onishi (1967) did not clarify the mechanism, it is apparent that this accumulation of Dxylonic acid by P. quercuum must be attributed to absence or low efficiency of the systems mediating its complete oxidation. The possibility that other yeasts might metabolize D-xylose via an oxidative pathway involving the formation of D-xylonate, nevertheless, exists. Since the verification of such a route relies on the availability of strains utilizing D-xylonate, this character was examined in a limited number of yeast strains capable of utilizing Dxylose.
Material and Methods The strains studied (listed under Results) are held by the Yeast Division of the Centraalbureau voor Schimmelcultures in Delft (The Netherlands). For further details, reference is made to the 1987 CBS List of Cultures.
The utilization of D-xylonate as sole source of carbon by these strains was examined by the standard method described by Van der Walt and Yarrow (1984), using 6.8 g anhydrous potassium D-xylonate per 6.7 g Difco Yeast Nitrogen Base. Tubes were incubated at 25°C on a Tissue Culture Roller Drum (New Brunswick) rotating at 40 rph. The strains of Bullera alba and Bullera singularis were grown at 20°C because of their lower optimal growth temperature. Results were scored after 3, 7 and 14 days. When maximum growth occurred after 7 days, utilization was rated as delayed (D). The results are given in Table 1.
Results Results are given in Table
1.
Discussion The results in Table 1 is the first report confirming Dxylonate utilization by strains of divergent yeast species utilizing D-xylose. Of the 14 species tested, six utilized Dxylonate. These comprise the ascomycetous taxa Candida acuta Goto, Candida edax Van der Walt et Nel, Zygozyma arxii Van der Walt et a1. as well as the basidiomycetous taxa Bullera alb Hanna (Derx), Bullera singularis (Phaff et Do Carmo-Sousa), Rodrigues de Miranda and Cryptococcus amylolentus (Van der Walt et
D-xylonate Utilization by Yeasts
al.l Golubev. While these strains could conveniently serve for the elucidation of the possibly novel, oxidative pathway from D-xylose in yeasts, the utilization of D-xylonate
Table 1. Utilization of D-xylonate by D-xylose-utilizing yeasts Strains
D-Xylose 1
Utilization of: XylitoP D-Xylonate
Ambrosiozyma monospora CBS 2554
+
+
Bullera alba CBS 501 singularis CBS 501
+ +
+
D D
Candida acuta CBS 7053 boidinii CBS 2428 edax CBS 5657 homilentoma CBS 6312 utilis CBS 9950
+ + + + +
+ + + + +
+
Cryptococcus amylolentus CBS 6039
+
+
+
Debaryomyces hansenii CBS 767
+
+
Geotrichum eriense CBS 5974
+
+
Hormoascus ambrosiae CBS 6003
+
+
Pichia stipitis CBS 5773
+
+
Zygozyma arxii CBS 7333
+
1
Data from Barnett et al. (1983)
193
itself must, at present, only be considered as presumptive of such route; the ability to utilize D-xylonate does not of necessity imply the presence of the specific dehydrogenase mediating the conversion of D-xylose to either xylono-ylactone or xylono-6-lactone. The failure of the D-xyloseutilizing strains to metabolize D-xylonate could be due to the absence of systems mediating either its transport into the cell, or further oxidation via as yet undetermined intermediates. Given the distinctive route for the metabolism of D-xylonate, which precludes this compound entering the pentose cycle as D-xylulose-S-phosphate, the utilization of D-xylonate could carry sufficient weight as a physiological differentia for discriminating yeast species - notably among D-xylose utilizing taxa. Acknowledgement. The authors thank Dr. R. M. Horak for the gift of potassium D-xylonate.
+
References Barnett, j. A., Payne, R. W., Yarrow, D.: Yeasts: characteristics
+
and identification. Cambridge, Cambridge University Press 1983 Buchert, j., Viikari, L.: Oxidative D-xylose metabolism of Gluconobacter oxidans. App!. Microbio!. Biotechno!' 29, 375-379 (1988) Suzuki, T., Onishi, H.: The production of xylitol and D-xylonic acid by yeasts. Agr. Bio!. Chern. Oapan) 31, 1233-1236 (1967) Van der Walt, J. P., Yarrow, D.: Methods for isolation, maintenance, classification and identification of yeasts, pp. 45-104. In: The Yeasts, a taxonomic study (N. j. W. Kreger-van Rij, ed.), 3rd ed. Amsterdam, Elsevier, Science Pub!. BV 1984
Prof. Dr. j. P. Van der Walt, Department of Microbiology and Biochemistry, University of the Orange Free State, P.O. Pox 339, Bloemfontein 9300, South Africa
14 System. Appl. Microbiol. Vol. 13/2