International Journal of Systematic and Evolutionary Microbiology (2015), 65, 2968–2974
DOI 10.1099/ijs.0.000363
Cyberlindnera xylosilytica sp. nov., a xylitolproducing yeast species isolated from
lignocellulosic materials
Raquel M. Cadete,1 Monaliza A. M. Cheab,1 Renata O. Santos,1 Silvana
V. B. Safar,1 Jerri E. Zilli,2 Marcos J. S. Vital,3 Luiz C. Basso,4 Ching-Fu Lee,5
Cletus P. Kurtzman,6 Marc-André Lachance7 and Carlos A. Rosa1
Correspondence
Carlos A. Rosa
[email protected]
1
Departamento de Microbiologia, ICB, C.P. 486, Universidade Federal de Minas Gerais,
Belo Horizonte, MG, 31270-901, Brazil
2
Embrapa Agrobiologia, Seropédica, RJ, Brazil
3
Departamento de Biologia, Universidade Federal de Roraima, Campus do Paricarana, Boa Vista,
Brazil
4
Departamento de Ciências Biológicas, Escola Superior de Agricultura Luiz de Queiroz,
Universidade de São Paulo, Piracicaba, São Paulo, Brazil
5
Department of Applied Science, National Hsinchu University of Education, Hsinchu, 300 Taiwan,
ROC
6
Bacterial Foodborne Pathogens and Mycology Research Unit, National Center for
Agricultural Utilization Research, Agricultural Research Service, US Department of Agriculture,
Peoria, IL, USA
7
Department of Biology, University of Western Ontario, N6A 5B7 London, Ontario, Canada
Independent surveys of yeasts associated with lignocellulosic-related materials led to the
discovery of a novel yeast species belonging to the Cyberlindnera clade (Saccharomycotina,
Ascomycota). Analysis of the sequences of the internal transcribed spacer (ITS) region and the
D1/D2 domains of the large subunit rRNA gene showed that this species is related to C.
japonica, C. maesa and C. easanensis. Six isolates were obtained from different sources,
including rotting wood, tree bark and sugar cane filter cake in Brazil, frass from white oak in the
USA and decayed leaf in Taiwan. A novel species is suggested to accommodate these isolates,
for which the name C. xylosilytica sp. nov. is proposed. The type strain of C. xylosilytica sp. nov.
is NRRL YB-2097T (5CBS 13984T5UFMG-CM-Y347T) and the allotype is UFMG-CM-Y409
(5CBS 14083). The novel species is heterothallic and complementary mating types are
represented by the type and allotype strains. The MycoBank number is MB 811428.
The genus Lindnera was proposed by Kurtzman et al. (2008)
to accommodate yeast species initially classified in the genera
Pichia and Williopsis. The genus name Lindnera is also a
validly published name for a plant genus, and Minter
(2009) proposed to transfer the species assigned to this
genus to Cyberlindnera as new combinations. The members
included in the genus show noticeable differences in ascospore morphology (spherical, hat-shaped or Saturn-shaped)
Abbreviation: ITS, internal transcribed spacer
The GenBank/EMBL/DDBJ accession numbers for the partial
sequence of the LSU rRNA gene (including D1/D2 domains) and ITS
region of strain NRRL YB-2097T are EF550324 and KP232976,
respectively.
2968
and include both hetero- and homothallic species. Glucose
is fermented by all species, and most species assimilate
many of the carbon sources included in standard assimilation tests (Kurtzman, 2011).
Since the last yeast taxonomic treatise (Kurtzman et al.,
2011), novel species of Cyberlindnera have been described,
such as Lindnera (Cyberlindnera) rhizosphaerae (Mestre
et al., 2011), Lindnera (Cyberlindnera) wuzhiensis (Wang
& Bai, 2010), C. samutprakarnensis (Poomtien et al.,
2013) and C. xylebori (Ninomiya et al., 2013). Other species
recently described as C. mengyuniae, C. adriatica, C. maesa,
C. takata, C. taoyuanica, C. hungchunana and C. stauntonica also belong to the Cyberlindnera clade (Chen et al.,
2009; Čadež et al., 2012; Chang et al., 2012). Despite the
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Cyberlindnera xylosilytica sp. nov.
discovery of such an impressive number of novel species,
the biotechnological properties of the majority of yeasts
within the Cyberlindnera clade, with few exceptions, are
still unknown. Recently, Kamat et al. (2013) reported the
production of xylitol, a polyol showing wide applications
in a variety of industries, such as food and pharmaceuticals,
by C. saturnus. Also, xylitol production by strains of C. rhodanensis and C. saturnus was lately observed (Junyapate
et al., 2014). Currently, xylitol is produced through the
reduction of xylose, a pentose carbon source, obtained
from chemical hydrolysates of lignocellulosic materials
(Mohamad et al., 2015). The drawbacks of this process
are a low initial availability of sugar and harsh non-ecofriendly purification and separation steps with only 50–
60 % conversion of xylose to xylitol (Dhiman et al.,
2008). Alternatively, since yeasts are known to be excellent
xylitol bioproducers, the microbial conversion of xylose by
yeasts offers a greener and more economically feasible
option for the achievement of this high-value added product (Kamat et al., 2013; Mohamad et al., 2015). Thus, the
description of novel yeast species or strains able to convert
xylose to xylitol at high rates should receive attention.
During surveys of yeast communities associated with rotting wood and tree barks from the Amazon rainforest in
the Brazilian state of Roraima, and with sugar cane filter
cakes from alcohol and sugar distilleries in Brazil, four
yeast isolates were thought to represent a novel species of
the genus Cyberlindnera. Analysis of the D1/D2 variable
domain of the LSU rRNA gene indicated that the strains
represent a novel species whose closest ascosporic relative
is C. japonica. The D1/D2 sequences of the Brazilian strains
were almost identical to those of strain NRRL YB-2097,
obtained from frass collected from a white oak in the
USA, and of strain NU1W51, isolated from decayed
leaves in Taiwan. The six strains examined exhibit one
polymorphism in the D2 domain. The name C. xylosilytica
sp. nov. is proposed to accommodate these strains, given
their ability to consume the wood sugar D -xylose.
Yeast isolation and identification
Among the six strains identified as representatives of the
novel species, three were isolated from rotting wood and
tree bark samples from the Brazilian Amazon rainforest.
The rotting wood samples were collected in the municipality of São João da Baliza, state of Roraima, Northern Brazil,
in October 2009 (Cadete et al., 2012). The samples were
cultured in flasks with YNB-D -xylose medium (yeast nitrogen base 0.67%, D -xylose 0.5%, chloramphenicol 0.02%)
or YNB-xylan medium (yeast nitrogen base 0.67%, xylan
1%, chloramphenicol 0.02%) and incubated at 25 uC
with stirring at 150 r.p.m. until detection of growth
(3–10 days), as previously described (Cadete et al., 2012).
Two strains, UFMG-CM-Y309 (5UFMG-HMD-7.2) and
UFMG-CM-Y407 were both obtained from samples
cultured on YNB-xylan medium. Strain UFMG-CM-Y408
(5 UFMG-C165) was isolated from tree bark collected in
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January 2012 in the ecological reserve of Serra da Prata,
located in the municipality of Mucajaı́, Roraima state.
The tree bark sample was cultured in flasks with YNBraffinose-ethanol medium (yeast nitrogen base 0.67%, raffinose 1%, ethanol 8% and chloramphenicol 0.02%) and
incubated at 30 uC without shaking until detection of
growth (up to 30 days). Strain UFMG-CM-Y409 was isolated from a sugar cane filter cake (a residue from the treatment of sugar cane juice by filtration) sample collected in
an ethanol distillery in the municipality of Iracemópolis,
São Paulo state, in December of 2010. This strain was collected and cultured in YNB-D -xylose medium in the
conditions described for processing the rotting wood
samples. Strain NU1W51 was obtained from a decayed
leaf sample collected in Liougeui, Kaohsiung, Taiwan in
June 2009, as described by Lee et al. (2009). Finally, the
type strain, NRRL YB-2097T, was isolated from insect frass
collected in July 1950 from a white oak (Quercus alba) growing in Waterloo, South Carolina, USA (Kurtzman et al.,
2008). All the strains were stored at 280 uC for further
identification.
The yeasts were characterized using standard methods
(Kurtzman et al., 2011). Species identification was performed by analysis of the D1/D2 variable domains and the
ITS-5.8S region of the large subunit of the rRNA gene, as
described previously (White et al., 1990; O’Donnell, 1993;
Lachance et al., 1999). The amplified DNA was concentrated,
cleaned and sequenced in an ABI 3130 Genetic Analyzer
automated sequencing system using BigDye v3.1 and POP7
polymer. The sequences were assembled, edited and aligned
with the program MEGA6 (Tamura et al., 2013). Phylogenetic
placement of the novel species was based on neighbourjoining analysis of the sequences of the D1/D2 domains of
the large subunit rRNA gene. The bootstrap consensus tree
was produced from 1000 iterations using 563 aligned
nucleotide positions.
Xylitol production assays
The potential for xylitol production by some species of
Cyberlindnera has already been demonstrated in previous
works (Kamat et al., 2013; Junyapate et al., 2014). In this
study, the yeasts were isolated from lignocellulose-related
substrates, which contain xylose, and in some cases, enrichment steps were used where the media contained xylose or
xylan (a homopolymer of xylose) as sole carbon sources.
For these reasons, xylose culture assays to ascertain the production of xylitol were carried out with the strains isolated
in Brazil and the type strain. Strain NU1W51 was not available for evaluation at the time of these tests. Yeast inocula
and batch xylose culture experiments were conducted as
described previously (Cadete et al., 2012). Cells were cultured in 50 ml YPX (10 g yeast extract l21; 20 g peptone
l21; 30 g D -xylose l21) medium in 125 ml Erlenmeyer
flasks with continuous shaking (200 r.p.m.) at 30 uC for
24 h. D -Xylose and yeast extract–peptone solutions were
sterilized separately. Cells were recovered by centrifugation,
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R. M. Cadete and others
washed twice and resuspended in cultivation medium to a
final concentration of 0.05 g l21. The experiments were carried out in 100 ml YPX medium (10 g yeast extract l21; 20 g
peptone l21; 50 g D -xylose l21) in 250 ml Erlenmeyer flasks
incubated as described above for 72 h. Samples were taken
at 0, 24, 48 and 72 h and stored at 220 uC until analysis.
Cell concentrations were determined in a spectrophotometer by optical density at 600 nm, using a previously
determined calibration curve (dry weight|OD600). Afterwards, all samples were centrifuged and the resulting supernatants were diluted and filtered using a Sep-Pak C18
(Millipore) filter. Levels of xylose, xylitol, ethanol, glycerol
and acetic acid were determined by HPLC (Shimadzu) with
an Aminex HPX-87H ion exchange column (Bio-Rad) and a
refractive index detector (RID-6A, Shimadzu). The mobile
phase was 5 mM H2SO4, at a flow rate of 0.6 ml, 45 uC,
with a sample injection volume of 20 ml. The parameters
xyl
xyl
21
Y p=s (g g21, xylitol yield), Y et
p=s (g g , ethanol yield), Q p
21 21
(g l21 h21, xylitol productivity) and Q et
h , ethanol
p (g l
productivity), and the sugar consumption (%), cell biomass,
xylitol and ethanol concentration (g l21) were determined
experimentally as outlined by Cadete et al. (2012).
Species delineation and phylogenetic placement
The novel species belongs to the Cyberlindnera clade and is
most closely related to the ascosporic species C. japonica, C.
maesa and C. easanensis based on a phylogeny inferred
from large subunit rRNA gene D1/D2 sequences (Fig. 1).
The six strains examined exhibit one polymorphism in
the D2 domain and differ by 5–9 substitutions from
other subclade members, which is comparable to the 6–9
substitutions that separate the three described subclade
members. Sequences of the ITS region of the isolates of
the novel species were identical. The novel species differs
by 17 substitutions and 15 gaps in ITS sequences from C.
easanensis. The ITS sequences of the other related species
were not available for identity comparison. On this basis,
we propose the novel species C. xylosilytica sp. nov.
When mixed in pairs on 5% malt extract agar cultures,
NRRL YB-2097 (h+) and UFMG-CM-Y409 (h2) produced
asci with hat-shaped ascospores. This result suggests that
the novel species is heterothallic. Cultures of paired complementary mating types form asci with two to four hatshaped ascospores. Asci were deliquescent, and ascospores
were observed after 3–5 days at 25 uC (Fig. 2). The other
isolates (UFMG-CM-Y309, 407 and 408) did not produce
ascospores when mixed in pairs with the other strains or
individually on diluted V8 agar, Fowell acetate, cornmeal
agar or yeast carbon base agar supplemented with 0.01%
ammonium sulphate incubated at 15 uC and 25 uC until
21 days. Strain NU1W51 did not produce ascospores
when tested individually under the same conditions.
The isolation of this novel species from diverse sources
associated with lignocellulosic substrates in different
regions of Brazil and also in the USA and Taiwan suggests
2970
that the lignocellulose and related materials could be its
ecological niche. The close relatives of this novel yeast
species – C. japonica, C. maesa and C. easanensis – have
been isolated from frass samples collected in insect tunnels
in fir trees, trees (fir and oak) and phylloplane (Kurtzman
et al., 2011; Chang et al., 2012), suggesting an adaptation of
these yeasts to these particular habitats.
The strains of C. xylosilytica sp. nov. are physiologically
similar to strains of C. japonica, C. maesa and C. easanensis,
but can be distinguished from them based on growth on
N-acetyl-D -glucosamine and fermentation of sucrose,
which are positive for the novel species and negative for
the other species.
Description of C. xylosilytica sp. nov. Cadete, Lee,
Kurtzman, Zilli, Vital, Lachance & Rosa
C. xylosilytica (xy.lo.si.ly9ti.ca. N.L. neut. n. xylosum xylose;
Gr. adj. lyticos able to dissolve; N.L. fem. adj. xylosilytica
xylose-dissolving).
In 5% malt extract agar after 3 days at 25 uC, the cells are
spherical to ovoid (1.3–3.8|2.0–4.5 mm), and occur singly
or in pairs. Budding is multilateral. In yeast extract (0.5%)glucose (2%) broth after a month, a sediment and a ring
are formed, but no pellicle is observed. On yeast extractmalt extract agar (YM agar) after 2 days at 25 uC, colonies
are greyish-white, mucoid, glistening and flat. In Dalmau
plates after 2 weeks on cornmeal agar, pseudohyphae are
present. Cultures of individual strains grown on Fowell
acetate, cornmeal agar, diluted (1: 9) V8 agar, 5% malt
extract agar and yeast carbon base agar supplemented
with 0.01% ammonium sulphate incubated at 15 uC and
25 uC until 21 days produce no ascospores. When mixed
in pairs on 5% malt extract agar cultures, strains NRRL
YB-2097T (h+) and UFMG-CM-Y409 (h2) produce asci
with two or four hat-shaped ascospores (Fig. 2).
At maturity, asci become deliquescent. Fermentation of
glucose and sucrose are positive. Xylose fermentation is
negative using Durham tubes, but ethanol is produced
from xylose when determined by HPLC. Maltose and trehalose are not fermented. Assimilation of carbon compounds: glucose, sucrose, raffinose (variable), melibiose
(variable), galactose (variable), trehalose (variable and
slow), maltose, melezitose, cellobiose, salicin, L -rhamnose,
D -xylose, L -arabinose (variable), ethanol, glycerol, D -mannitol, D -glucitol, DL -lactate, succinate, D -gluconate, N-acetylD -glucosamine (slow), xylitol and ethylacetate. No growth
occurs on inulin, lactose, soluble starch, L -sorbose, D -arabinose, D -ribose, methanol, erythritol, ribitol, galactitol, myoinositol, citrate, hexadecane, acetone or 2-propanol. Assimilation of nitrogen compounds: positive for lysine and negative
for nitrate and nitrite. Growth in amino-acid-free medium
is positive. Growth at 37 uC and 40 uC is positive. Growth
on YM agar with 10% sodium chloride is variable. Growth
in 50% glucose/yeast extract (0.5%) is negative. Acid production is positive. Starch-like compounds are not produced.
In 100 mg cycloheximide ml21, growth is negative. Urease
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Cyberlindnera xylosilytica sp. nov.
Cyberlindnera xylosilytica NU1W51 (HM461705)
0.01
58 Cyberlindnera xylosilytica UFMG-CM-Y309 (JQ695900)
88
Cyberlindnera xylosilytica UFMG-CM-Y409 (KP698383)
Cyberlindnera xylosilytica UFMG-CM-Y407 (KP698382)
Cyberlindnera xylosilytica NRRL YB-2097T (EF550324)
62 Cyberlindnera xylosilytica UFMG-CM-Y408 (KC206088)
51
Candida maesa ATCC MYA-4698T (JQ812697)
Candida easanensis JCM 12477T (AY634571)
Cyberlindnera japonica NRRL YB-2750T (EF550323)
Cyberlindnera amylophila NRRL YB-1287T (EF550319)
98
Cyberlindnera mississippiensis NRRL YB-1294T (EF550320)
Cyberlindnera veronae NRRL Y-7818T (EF550322)
Cyberlindnera fabianii NRRL Y-1871T (EF550321)
Candida pattaniensis JCM 12475T (AY634568)
Candida adriatica ZIM 2334T (HE574661)
93
57
Candida hungchunana ATCC MYA-4701T (JQ812700)
Candida taoyuanica ATCC MYA-4700T (JQ812699)
Cyberlindnera euphorbiiphila NRRL Y-12742T (EF550312)
Candida stauntonica ATCC MYA-4699T (JQ812698)
Candida maritima NRRL Y-17775T (EF550332)
70
Candida mycetangii NRRL Y-6843T (EF550330)
Candida nakhonratchasimensis JCM 12474T (AY634567)
Cyberlindnera americana NRRL Y-2156T (EF550328)
Cyberlindnera bimundalis NRRL Y-5343T (EF550329)
Cyberlindnera euphorbiae NRRL Y-17232T (EF550326)
Cyberlindnera meyerae NRRL Y-17236T (EF550327)
74
Cyberlindnera maclurae NRRL Y-5377T (EF550310)
Cyberlindnera jadinii NRRL Y-1542T (EF550309)
Cyberlindnera petersonii NRRL YB-3808T (EF550311)
Cyberlindnera xylebori NBRC 11048T (AB534167)
50
Candida mengyuniae JHLT (EU043158)
Cyberlindnera samutprakarnensis JP52T (AB598079)
Cyberlindnera lachancei NRRL Y-27008T (EF550313)
Cyberlindnera misumaiensis NRRL Y-7686T (EF550248)
99
Candida sp. NRRL Y-27103 (EF550307)
Candida takata ATCC MYA-4702T (JQ906764)
80
Candida vartiovaarae NRRL Y-6701T (EF550315)
T
66 Cyberlindnera sargentensis NRRL YB-4139 (HM461618)
50
80
Cyberlindnera suaveolens NRRL Y-17391T (EU544674)
88
Cyberlindnera saturnus Y-17396T (EF550316)
Cyberlindnera mrakii NRRL Y-1364T (EF550317)
Cyberlindnera subsufficiens NRRL Y-1657T (EF550318)
Wickerhamomyces anomalus NRRL Y-366T (EF550341)
99
Wickerhamomyces hampshirensis NRRL YB-4128 (EF550334)
Fig. 1. Neighbour-joining phylogenetic tree showing the placement of C. xylosilytica sp. nov. among species of the Cyberlindnera clade based on LSU rRNA gene D1/D2 domain sequences. Numerals represent percentages from 1000 replicate
bootstrap resamplings. Bar, 0.01 substitutions per nucleotide position.
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R. M. Cadete and others
(a)
(b)
Fig. 2. Budding cells, conjugated cells, asci and hat-shaped ascospores of C. xylosilytica sp. nov. NRRL YB-2097 (h+)
6 UFMG-CM-Y409 (h2) on 5 % malt extract agar after 5 days at 25 8C. (a) budding cells, conjugated cells and asci with
hat-shaped ascospores; (b) budding cells, asci with hat-shaped ascospores and released ascospores. Bars, 5 mm.
activity is negative. Diazonium Blue B reaction is negative. The
habitats are lignocellulose substrates collected in different
regions of Brazil, in the USA and also in Taiwan.
The type strain accession number of C. xylosilytica sp. nov.
is NRRL YB-2097T (h+). It was isolated from frass collected
in white oak in the state of South Carolina, USA. It has been
deposited in the ARS Culture Collection, National Center
for Agricultural Utilization Research, Peoria, IL, USA and
is permanently preserved in a metabolically inactive state.
An ex-type culture has been deposited in the collection of
the Yeast Division of the Centraalbureau voor Schimmelcultures (CBS), Utrecht, the Netherlands, as strain CBS 13984T,
and in the Collection of Microorganisms, DNA and Cells of
Federal University of Minas Gerais (Coleção de Microorganismos, DNA e Células da Universidade Federal de
Minas Gerais, UFMG), Belo Horizonte, Minas Gerais,
Brazil, as strain UFMG-CM-Y347T. The designated allotype, UFMG-CM-Y409 (h2) (5CBS 14083) was isolated
from sugar cane filter cake sample collected in an ethanol
distillery in Brazil. The MycoBank number is MB 811428.
Production of xylitol by C. xylosilytica
To evaluate the conversion of xylose and the production of
xylitol, the five yeast strains were subjected to a culture
assay in YPX medium containing 50 g xylose l21. The D xylose consumption, xylitol yield and productivity and
cell biomass, xylitol and ethanol concentration are summarized in Table 1. The results were calculated based on
the time of maximum xylitol production achieved or the
time until the end of the experiment.
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All strains produced xylitol from xylose as sole carbon
source and the polyol was the main product attained from
the metabolism of the pentose, since low ethanol concentrations were obtained. As shown in Table 1, all strains
achieved maximum xylitol production at 72 h (time of the
end of the experiment). The consumption of xylose was
high among all the strains, ranging from approximately 86
to 94%. In general, considering the deviation values, the
amount of xylitol produced was approximately the same
among the isolates, with an mean production equal to
33.02 g l21. The high xylitol titres observed reflected the
great yields and productivities attained, being, on average,
xyl
Y p=s ¼ 0:726 g g21 (corresponding to a conversion efficiency
of xylose to xylitol of 80%) and Qp ¼ 0:459 g l21 h21 . Conversely, poor ethanol production was observed (1.45 g l21 on
average), corresponding to a conversion efficiency of 6%.
xyl
Comparing these results with those of previous studies of
other members of the Cyberlindnera clade, C. xylosilytica presented the best xylitol yields so far. Junyapate et al. (2014)
xyl
reported Y p=s values for three strains of C. rhodanensis and
two of C. saturnus equal to 0.16, 0.27, 0.33, 0.13 and
0.17 g g21, respectively, in medium with xylose as sole
carbon source. No information about the production of
ethanol by these yeasts has been provided by these authors.
Kamat et al. (2013) subjected a strain of C. saturnus to fermentation assays at a range of 5–150 g xylose l21. With an
initial concentration of 50 g xylose l21 (the same as that
used in the present work), at 72 h C. saturnus F12 had consumed &30 g l21 xylose (60% of the initial concentration)
and showed a xylitol production of &15 g l21, thus presenting yield and productivity values equivalent to 0.49 g g21
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Cyberlindnera xylosilytica sp. nov.
Table 1. Production of xylitol from D -xylose in YPX medium by C. xylosilytica sp. nov.
Yeast
strain
xyl
xyl
consumption
(%)*
Cell
biomass
(g l21)
Maximum
xylitol
(g l21)
Y p=s
(g g21)†
Qp
(g l h21)‡
Ethanol
(g l21)
Y et
p=s
(g g21)†
Q et
p
(g l h21)‡
Time
(h)§
91.3
91.2
86.1
94.3
90.6
3.50 ^ 0.11
3.39 ^ 0.15
2.46 ^ 0.16
3.59 ^ 0.24
3.37 ^ 0.15
30.33 ^ 3.73
34.33 ^ 0.03
32.26 ^ 2.08
34.46 ^ 0.77
33.73 ^ 0.08
0.686
0.737
0.753
0.720
0.734
0.421
0.477
0.448
0.479
0.468
1.53 ^ 0.62
1.10 ^ 0.02
1.11 ^ 0.01
2.39 ^ 0.09
1.12 ^ 0.07
0.034
0.023
0.026
0.050
0.034
0.021
0.015
0.015
0.033
0.016
72
72
72
72
72
D -Xylose
NRRL Y-2097T
UFMG-CM-Y309
UFMG-CM-Y407
UFMG-CM-Y408
UFMG-CM-Y409
21
21
*D -xylose consumption (%) – percentage of xylose consumed from the initial concentration.
xyl
21
†Y p=s (g g21) and Y et
p=s (g g ) – xylitol or ethanol yield: correlation between xylitol or ethanol (DP) produced with xylose (DS) consumed.
21 21
h ) – xylitol or ethanol productivity: ratio between xylitol or ethanol concentration (g l21) and time (h).
‡Qp (g l21 h21) and Qet
p (g l
§Time of maximum xylitol production (g l21) reached or end of the experiment.
xyl
and 0.21 g l21 h21, respectively. Neither ethanol nor any
other sugar alcohol was detected when C. saturnus was
grown on xylose (Kamat et al., 2013). Comparing the ethanol
production observed for C. xylosilytica sp. nov. with a strain
of Scheffersomyces stipitis tested under the same conditions
(Cadete et al., 2012), production of ethanol by the novel
species was very low. Scheffersomyces stipitis NRRL Y-7124T
21
was able to produce 15 g ethanol l21 (Y et
p=s ¼ 0:35 g g
et
21 21
and Qp ¼ 0:62 g l h ) at 24 h, a far greater value than
found in this study. Therefore, the results attained for C.
xylosilytica open prospects for the exploitation of this novel
species towards the optimization of its xylitol production,
applying different culture conditions and xylose-rich substrates, such as lignocellulosic hydrolysates.
molendinolei sp. nov., two yeast species isolated from olive oil and
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Acknowledgements
This work was funded by Conselho Nacional de Desenvolvimento
Cientı́fico e Tecnológico (process 560715/2010-2), Fundação do
Amparo a Pesquisa do Estado de Minas Gerais (APQ-01347-12 and
CBB - RDP-00094-10), the Financiadora de Estudos e Projetos (process
2084/07), Coordenação de Aperfeiçoamento de Pessoal de Nı́vel
Superior (Procad-NF, process 2280/2008), the Ministry of Science
and Technology, Taiwan (NSC 100-2621-B-134-001) and the Natural
Science and Engineering Research Council of Canada (M. A. L.). The
mention of trade names or commercial products in this publication is
solely for the purpose of providing specific information and does not
imply recommendation or endorsement by the US Department of Agriculture. The US Department of Agriculture is an equal opportunity provider and employer.
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