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1.
Jacqueline Rebello Masao Ohno Hiroyuki Ukeda Masayoshi Sawamura 《Journal of applied phycology》1996,8(6):517-521
Six economically important species ofGracilaria, from a number of commercial sources around the world, andGracilariopsis lemaneiformis, collected from two Japanese localities, were used as the sources of raw material for the evaluation of agar quality. Agar-agar was extracted by pretreatment with various concentratrions of NaOH (0%, 3%, 5%, 7%, 10%) incubated at 80 °C for 2 h. Agar yield, viscosity, dynamic gelling and melting temperature and gel texture were determined for 1.5% agar gels. The highest agar yield was obtained fromG. gracilis from Argentina (39.5%), while the lowest was from BrazilianG. gracilis (13.37%). Dynamic gelling temperature was highest in the agar fromG. gracilis from Turkey (59 °C) and lowest in the non-alkali treated agar isolated fromG. edulis from Indonesia (46 °C). Melting temperature ranged from 96 °C in the agars from the JapaneseGracilariopsis andG. chilensis from Chile to 69 °C in the non-alkali treated agar fromG. edulis from Indonesia. In general, all species produced an agar with high gel strength after treatment with 5% NaOH, except forG. chilensis and the twoGracilariopsis species, which produced an agar with high gel strength after treatment with 3, 7 and 10% NaOH. The highest gel strength (2056 ± 13.6 cm–2) and hardest gel (261 ± 19.89 g mm–2) were obtained fromG. lemaneiformis from Japan (Oita Prefecture) after treatment with 7 and 10% NaOH respectively. The lowest gel strength (351 ± 93 cm–2) was obtained fromG. gracilis from Brazil after treatment with 3% NaOH. The softest gel (66.31 ± 9.63 g mm–2) was isolated fromG. tenuistipitata from China, after treatment with 3% NaOH. The most flexible gel (11.62 ± 0.31 g mm–2 × 102) was obtained fromG. chilensis from Chile after treatment with 3% NaOH.Author for correspondence 相似文献
2.
Dora Luz Arvizu-Higuera Y. Elizabeth Rodríguez-Montesinos J. Iván Murillo-Álvarez Mauricio Muñoz-Ochoa Gustavo Hernández-Carmona 《Journal of applied phycology》2008,20(5):515-519
The effects of alkali treatment time and extraction time of native agar and alkali treated agar obtained from Gracilaria vermiculophylla were studied. The response characteristics were mainly agar yield and gel strength. Alkali treatment was carried out at 0.5,
1.0, 1.5, 2.0, 2.5, and 3.0 h. Agar yield and gel strength decreased with the increase in the time of the alkali treatment.
The highest yield (15.3%) and highest gel strength (1,064 g cm−2) were obtained at 0.5 h, and therefore this time was used for the next experiment. The extraction of both native and alkali
treated agars was carried out at 1.5, 2.0, 2.5, and 3.0 h. The best extraction time for alkali treated agar was 1.5 h, and
for native agar 2.5 h. The alkali treated agar obtained with the different alkali treatment and extraction times showed higher
melting (92.4–99.7°C) and gelling (35.7–39.6°C) temperatures. Native agar was lower in melting (60.2–64.1°C) and gelling (20.4–23.4°C)
temperatures. The 3,6-anhydrogalactose content decreased with increasing alkali treatment time, with the opposite effect during
the extraction of native and alkali treated agars. 相似文献
3.
Optimization and scale-up of a new photobleaching agar extraction process from Gracilaria lemaneiformis 总被引:1,自引:0,他引:1
Haiyan Li Jianyu Huang Yanjuan Xin Biaoming Zhang Yan Jin Wei Zhang 《Journal of applied phycology》2009,21(2):247-254
An eco-friendly photobleaching extraction process for agar extraction from the red alga Gracilaria lemaneiformis was developed for the benefit of workers’ health and environmental safety. Here we report the optimization of key process
parameters (alkali modification concentration, photobleaching duration, algal length and screen filter opening size) in order
to scale up this new technique. The optimal conditions were found to be modification by 3–5% NaOH, photobleaching for 5 h,
using algal fragments 2 –4 cm in length, and a filter screen with a 6 μm opening. A 20-L agar extraction reactor was thus
constructed, and the scale-up of the agar extraction process was tested in six batch experiments. The resulting agar quality
was similar to that of the laboratory-scale extraction. In addition, batch-to-batch reproducibility was excellent. The results
demonstrate the excellent scale-up ability and potential application of this new photobleaching agar extraction process on
a commercial scale. The agar yield and gel strength for 5% NaOH modified agar were 26.8% and 1,897 g cm−2, while those for 3% NaOH modified agar were 28.2% and 1,287 g cm−2, respectively. It is clear that the agar yield and quality can be manipulated via alkali modification in this new eco-friendly
extraction to meet market demands. 相似文献
4.
The effect of alkali treatments on the yield, rheological and chemical properties of agar from Gracilaria cornea growing along
the Yucatáncoast were studied in order to evaluate its potential for industrial use inan attractive economic standpoint. Alkali
treatment was carried out with NaOH concentrations of 0.5%, 1%, 3% and 5% in a water bath at 80, 85 and 90 °C. Agar yield,
gel strength, gelling and melting temperatures, sulphate, 3,6-anhydro-galactose and ash content weredetermined. The different
combinations of NaOH concentration and treatment temperature strongly influenced agar characteristics. There was a variation
in the agar content for all NaOH treatments and temperature combinations, ranging between 14.5% to 22.1%. Although the yields
obtained for 0.5% NaOH at all temperatures and 1% NaOH at 80 and 85°C were higher than those required by the industry, the
physical and chemical characteristics of the agar were similar to those obtained fornative agar from the same species. The
gel strengths, sulphate content and gelation hysteresis obtained with agar from the 1% NaOH treatment at 90 °C are in the
range required by the food industry. Treatments with 3% and 5% NaOH at all temperatures improved significantly the agar quality
giving higher gel strengths (974–1758 g cm -2) than those reported for other Gracilaria species.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
This study aimed to develop agar extraction protocols for Gracilaria salicornia from Tanzania and investigate its physico‐chemical characteristics. A 33 factorial experimental design was used in the extraction of agar whereby three independent variables of NaOH concentration (10, 20 and 30% w/v), alkali pre‐treatment duration (0.5, 1 and 2 h) and extraction temperatures (115, 120 and 125°C) were used to determine the optimum conditions for production of high‐quality agar. Agar yield, gel strength, sulfate content, gelling and melting temperatures were evaluated as dependent variables. The optimal condition was observed at 30% NaOH concentration, 2 h alkali pre‐treatment duration and 120°C extraction temperature. The yield, gel strength, sulfate content, gelling and melting temperatures of the agar obtained under these conditions were 26.9 ± 0.7%, 510.3 ± 16.2 g cm?2, 0.29 ± 0.04%, 39.3°C and 88.4°C, respectively. These properties are very close to that of imported commercial agar. It was concluded that the local agar is capable of replacing imported agar for most general purposes. This offers a new possibility of using quality local agar in place of commercial agar. 相似文献
6.
Mario Antonio Vergara-Rodarte Gustavo Hernández-Carmona Y. Elizabeth Rodríguez-Montesinos Dora Luz Arvizu-Higuera Rafael Riosmena-Rodríguez Jesús Iván Murillo-Álvarez 《Journal of applied phycology》2010,22(6):753-759
Gracilaria vermiculophylla, from Baja California Sur, Mexico, was studied in order to determine the seasonal variation of yield and quality of native
and alkaline agar during 2007–2008. The highest alkaline agar yield was obtained in summer (17%) and the highest gel strength
in spring (1,132 g cm−2). The highest melting temperature was 98°C (winter). The highest gelling temperature was 68°C (summer). The values obtained
are within the range of the most important Gracilaria species harvested worldwide. During the agar extraction step, the best results were obtained after 30 min of alkali treatment
with sodium hydroxide (7%), after which the quality decreased significantly. We produced Colagar from G. vermiculophylla which consists of the seaweeds treated with sodium hydroxide and dried. The yield and quality of the agar obtained from the
Colagar shows stability in both yield and quality during 1 year of storage, suggesting that alkali treatment is a good method
of avoiding agar hydrolysis during storage. 相似文献
7.
Seasonal variation in the physical properties of agar and biomass of Gracilaria sp. (chorda type) from Tosa Bay,southern Japan 总被引:1,自引:1,他引:0
Plants of Gracilaria sp.(chorda type), which grow along the coast of Uranouchi Inlet in Tosa Bay, southern Japan, showed the highest biomass in the summer (26 °C to 31 °C) and spring season (15.1 °C to 24.9 °C). Maximum biomass was 6952 g m–2 in July, but gradually decreased in the autumn (30.5 °C in September to 20 °C in November) and winter (19.5 °C in December to 14.9 °C in February). Variation in yields and gel strength of the agars, were shown to depend on the time in the season. After alkali treatment (5% NaOH, 2 h) at three different temperatures (70, 80, and 90 °C), the agars showed gel strengths essentially that of commercial grade agars, with the best gel obtained at 80 °C. Maximum gel strength (1455 g cm–2 of 1.5% agar gel) occurred in winter when the biomass and agar yield were low. Minimum gel strength was in spring. Gel strength was inversely correlated with agar yield, but was positively correlated with apparent viscosity. Maximum viscosity was 40 cP. in December. Gelling temperatures, pH of 1.5% agar gel, and moisture content in agars showed little variation. 相似文献
8.
Chemical composition of agars from a newly reported Japanese agarophyte,Gracilariopsis lemaneiformis
Anong Chirapart Masao Ohno Hiroyuki Ukeda Masayoshi Sawamura Hirozo Kusunose 《Journal of applied phycology》1995,7(4):359-365
The chemical composition of agars from Gracilariopsis lemaneiformis, newly reported from Japan, was investigated. Native agars were isolated by a sequential extraction of plants in water at
22 °C and 100 °C, and in boiling 20, 40 and 60° ethanol. Agars in each extract were analyzed by chemical methods, 1H, 13C NMR; and IR spectroscopy. The highest yield of agar (total carbohydrate) was obtained from the 40° ethanol extract (55°).
Highest sulfate content was attained in non-alkali treated agars extracted with hot water (4.81°, DS 0.2). The 3,6-anhydrogalactose
content was highest in the 40° ethanol extract (36.1° in non-alkali treatment, 40.3° in alkali treatment). The highest methoxyl
content (6.51°, DS 0.66) was obtained in the 60° ethanol extract. The G. lemaneiformis agar is composed of the biological precursor to agarobiose repeating units and agarobiose containing 6-O-methyl agarobiose and a small amount of 2-O-methyl-α-l-galactopyranose residues. Alkali treatment improved the chemical quality of the agar fractions, which was comparable
with Japanese commercial agar and agarose. 相似文献
9.
Ramavatar Meena Kamalesh Prasad M. Ganesan A. K. Siddhanta 《Journal of applied phycology》2008,20(4):397-402
Gracilaria edulis, G. crassa, G. foliifera, and G. corticata are naturally occurring agarophytes of Indian waters. These agarophytes were evaluated for their agar contents using an improved
process recently reported by us (US Patent 2005/0267296A1). The effect of different concentrations of NaOH in the alkali treatment
was studied for optimizing the extraction conditions. These Gracilaria species of Indian waters produced agars, both native and alkali treated, with different properties confirming the heterogeneity
of the agar polymers in this genera, as one would expect. Among these, G. edulis and G. crassa produced agar polymers having high gel strengths of 490 ± 8.16 and 800 ± 15.4 g cm−2, respectively, with 8% NaOH treatment as opposed the low gel strength agars that have been reported in the literature to
date. 相似文献
10.
Javier Orduña-Rojas Karla Y. García-Camacho Priscila Orozco-Meyer Rafael Ríosmena-Rodríguez Isaí Pacheco-Ruiz José A. Zertuche-González Alf E. Meling-López 《Journal of applied phycology》2008,20(2):169-175
Agar properties of two potentially commercial important seaweeds from the Gulf of California were studied. Maximum yield in
Gracilaria vermiculophylla (45.7%) occurred during the summer months, coinciding with high water temperatures (31°C) whereas minimum yields (11.6%)
were obtained during the coldest months of the year when populations of this species diminish in the bay. Gracilariopsis longissima showed two yield peaks, one in spring and another in fall, before the maximum and minimum seawater temperatures. Gel strength
in native agar from the two species was low (<22.5 g cm−2) for most of the year. G. vermiculophylla native agar showed a slight increase in gel strength from June to August, which were the hottest months. Maximum value was
85 g cm−1 in August. Maximum gel strength in G. longissima was observed in October (91 g cm−1), and an unusual native agar with no detectable gel strength was observed in March and April samples. Gelling temperatures
range from 27.7 to 36.5°C in G. vermiculophyla and from 26.6 to 34.9°C in G. longissima, meanwhile melting points were 73.9 – 53.5°C and 75.5 – 56.6°C, respectively. Sulfate content was high, 6.3–13.9% in G. vermiculophylla and 1.9–11.9% in G. longissima, and on the other hand 3,6 anhydrogalactose content was low 12.1–26.7% and 9.1–23%, respectively compared to other species.
Results obtained showed that mean native agar yields of Gracilaria vermiculophylla and Gracilariopsis longissima from the Gulf of California are comparable to other tropical Gracilaria. However, the low gel strength, high sulfate content and low 3,6 anhydrogalactose content observed in the native agar extracted
from these species make this an agaroid, thus alternative methods of extraction should be used to evaluate the possibility
of commercial utilization of both species. 相似文献
11.
The effect of alkali pre-treatments on the properties of agar obtained from Gelidiella acerosa and Gelidium pusillum growing along the West and South coast of India was studied in order to evaluate its potential for industrial use. Agar samples
were extracted by hot water extraction and termed native agar, and alkali pre-treatment was carried out with various NaOH
concentrations e.g. 4%, 6%, 8%, 10% and 15%, to optimise the alkali concentration for preparation of alkali-treated agar.
Gelidiella acerosa and Gelidium pusillum produced superior quality agar polymers having greater gel strengths 2,000 ± 50 and 1,400 ± 50 g cm−2 and lower sulphate contents ≤0.30% and ≤0.50%, respectively, as opposed the low gel strength and high sulphate content agars
reported in the literature. Furthermore, the physicochemical properties of agars were identical with the commercially available
agars. The results of this study revealed that Indian agarophytes may be used for production of superior quality agar and
agaroses, which may be used for food and biological applications. 相似文献
12.
The effect of darkness and ammonia on Gracilariopsis lemaneiformis agar yield and quality was studied. Plants were cultivated under controlled conditions in the laboratory and fertilized with ammonia prior to a month storage in the dark. Starch inclusions are known to interfere with the mechanical properties of the isolated agar. The starch content of algal tissue and the activities of the floridean starch phosphorylase and -glucosidase were measured during this storage period as a way to follow the enhancement of starch degradation in the absence of light, and to measure the effect of darkness on the content and quality of the synthesized agar. The agar yield, gel strength, 3,6-anhydrogalactose, sulphate and starch content were considerably affected by this dark treatment. The values obtained reflect a pattern of optimization of agar quality when Gracilariopsis lemaneiformis was stored in the dark. The isolated agar following dark treatment is less contaminated by starch inclusions. This is shown by the improvement in the agar yield and quality, the nutrient status of the plant and the reduction of the starch content.Abbreviations DW:
Dry weight
- FW:
Fresh weight
- S:
Sulphate
- 3,6-AG:
3,6-anhydrogalactose
- GS:
Gel strenght at 1.5% concentration
- CX:
Cold extract at 25 °C
- A:
Autoclaved extract at 121 °C
- MW:
Molecular weight
- PFD:
Photon flux density 相似文献
13.
Agar extraction process was developed for Gracilaria cliftonii by investigating the effects of various extraction variables and alkali treatments on agar yield and properties. The tested variables were soaking time, soaking temperature, seaweed to water ratio of, extraction temperatures and extraction time. Alkali treatments were carried out in alkali concentrations of 1%, 2%, 3% and 5% in a water bath at 60, 70 and 80 °C prior to agar extraction. The results showed that agar yield was significantly affected by all the tested variables. The agar yield was maximised when extraction process was carried out with 1 h soaking time at 30 °C with seaweed to water ratio of 1:150 and extracted for 3 h at 100 °C. The alkali-temperature combinations significantly influenced agar yield and properties. Irrespective of temperature, alkali treatments at 3% and 5% significantly increased the gel strength. 相似文献
14.
Erminio Murano Renato Toffanin Svein Halvor Knutsen Bonaventura Focher Roberto Rizzo Sergio Paoletti 《Journal of applied phycology》1993,5(4):417-424
Steam explosion was investigated as a pretreatment step in the isolation of agar from the macroalgaGracilaria dura. As compared to conventional procedures, the yield of agar obtained using this method on alkali (Na2CO3) conditioned algal material was higher. Extractions performed first at 95 °C and then at 121 °C showed that the major fraction of the agar was extracted at 95 °C, independently of the pretreatment. The efficiency of sulphate hydrolysis during steam explosion ofG. dura previously conditioned in Na2CO3, was similar to that of a NaOH based alkali pretreatment. Except for a lower nitrogen content of the sample obtained after NaOH based alkali pretreatment and a higher 6-O-methyl--d-galactose content in the agar after steam explosion, the chemical composition of the agars showed no significant difference. Agars extracted after steam explosion had melting temperature, gel strength and apparent modulus of elasticity lower than those of corresponding native and alkali (NaOH) pretreated samples, but comparable to those of a commercial sample.Author for correspondence 相似文献
15.
The seasonal effects on yield and gel properties ofGelidium canariensis agar were investigated at two intertidal populations at the northern coast of Gran Canaria. Physical and rheological properties were measured in 1.5% w/v solutions after treatment with alkali. No significant differences were found on agar characteristics between the two sites studied. The highest yields were obtained during summer with a maximum in June (27.8%) and minimum during late autumn and winter (18–18.6%). Overall quality was highest in winter (November–January), when gel strength peaked above 850 g cm–2. The results showed an agar of industrial quality. 相似文献
16.
R. D. Villanueva A. M. M. Sousa M. P. Gonçalves M. Nilsson L. Hilliou 《Journal of applied phycology》2010,22(2):211-220
The utilization potential, in terms of agar production, of the invasive alga, Gracilaria vermiculophylla, collected at Ria de Aveiro, northwestern Portugal was investigated. The agar yield ranged from 15% to 33%, with pre-extraction treatment with alkali generally increasing the yield. The gel quality (gel strength and apparent Young’s modulus) was best (>600 g cm?2 and >1,000 kPa, respectively) when alkali treatment with 6% NaOH for 3.5 h was performed. At these pretreatment conditions, the effect of extraction time was also investigated and highest yield and best gel quality were obtained with a 2 h extraction time. By employing these extraction conditions, G. vermiculophylla can be a source of industrial food-grade agar. The structure of agar from G. vermiculophylla was determined through chemical techniques and FTIR and NMR spectrometry. It is mainly composed of alternating 3-linked d-galactose and 4-linked 3,6-anhydro-l-galactose, with methyl substitution occurring at 16–19 mol% of C-6 in 3-linked units and 2–3 mol% of C-2 in 4-linked units. A minor sulfation on C-4 of 3-linked units was also detected; while precursor units (6-sulfated 4-linked galactosyl moieties) were found in the native extract. 相似文献
17.
Al-Alawi AA Al-Marhubi IM Al-Belushi MS Soussi B 《Marine biotechnology (New York, N.Y.)》2011,13(5):893-899
Carrageenophyte red seaweed from Oman, Hypnea bryoides, extracted using three different processes: an aqueous, a mild alkaline, and a more vigorous alkaline extraction was investigated.
The resulting extract precipitated by alcohol was subject to chemical and rheological measurements. The total carbohydrate
[ranged from 36.78 to 41.65 g/100 g], and ash [39.04 to 43.11 g/100 g] were the most abundant components in H. bryoides and contrary to the two, lipid content was found at a minimum [ranging from 2.95 to 3.38 g/100 g]. Alkali treatment with
NaOH allowed complete conversion of kappa (κ) carrageenan form as detected by FTIR analysis. Total yield by alkali treatments
gave higher yields (33%) compared with aqueous treatments (12%). However, subsequent aqueous treatment produced mixed carrageenan
(μ and κ) with higher molecular weight compared with the alkali treatments which produced single carrageenan form (κ) with
molecular weight of 4.1 × 105 Da. The effects of thermal history on gel–sol and sol–gel transition were investigated by differential scanning calorimeter
(DSC) and rheology on a pure sample and 1.5% κ-carrageenan mixture added with 30 mM KCl. Transition temperatures from DSC
and rheology showed comparable results and were in good agreement with those previously reported. 相似文献
18.
Min‐Woo Kim Yong‐Su Song Yeon Soo Han Yong Hun Jo Myung Hyo Choi Young‐Kyu Park Seung Ho Kang Sun‐Am Kim Changyong Choi Woo‐Jin Jung 《Entomological Research》2017,47(5):279-285
Chitin and chitosan were extracted from all specimens of Type I and II two‐spotted field crickets (Gryllus bimaculatus) following chemical treatment with an acid and alkali. For chitin extraction, 2 N HCl and 1.25 N NaOH solutions were used to achieve demineralization and deproteinization, respectively. For chitosan extraction, 50 % NaOH (w/v) and 50 % NaOH (w/w) solutions were used to achieve deacetylation. Chitosan yielded from adult exoskeletons of G. bimaculatus in Test A of Type I was 1.76 and 8.40 % on a fresh weight (FW) and dry weight (DW) basis, respectively, after treatment with 50 % NaOH (w/v) at 95°C for 3 h. Furthermore, the chitosan yielded in Test D of Type II was 1.79 and 7.06 % on FW and DW basis, respectively, after treatment with 50 % NaOH (w/w) at 105°C for 3 h. The average yield of chitin and chitosan was 2.42 and 1.65 % on a FW basis, and 10.91 and 7.50 % on DW basis, respectively. The deacetylation (%) of chitosan extracted from adult exoskeletons in Tests A, B, C1, C2, D1, and D2 were 81.2 %, 14.5 %, 19.6 %, 90.7 %, 17.1 %, and 95.5 %, respectively. The viscosities of the chitosans extracted from adult exoskeletons in Tests A, C2, and D2 were 32.0, 21.6, and 62.4 cP (centi Poise), respectively. The molecular weight of chitosan from adult exoskeletons of G. bimaculatus was 308.3 kDa. Our results indicate that adult exoskeletons of G. bimaculatus could be used as a source of chitin and chitosan for use as functional additives in industrial animal feeds. 相似文献
19.
Miguel Ángel Hurtado Marlenne Manzano-Sarabia Enrique Hernández-Garibay Isaí Pacheco-Ruíz José A. Zertuche-González 《Journal of applied phycology》2011,23(4):727-734
The yield and quality of agar from Gelidium robustum from the main commercial harvest beds along the western coast of the Baja California Peninsula (Mexico) were evaluated within
a latitudinal range of about 800 km (31°47′N to 27°05′N). Samples from six locations, Bahía Todos Santos, El Rosario, Isla
de Cedros, Islas San Benito, Punta Eugenia, and Bahía Asunción, were analyzed. Bryozoan, protein, and agar content in the
seaweed were estimated. The agar quality was determined by the content of 3,6-anhydrogalactose, sulfate, gel strength, and
gelling and melting temperature. All the values of these variables were correlated and then with the satellite-derived data
of the sea surface temperature (SST), net primary production (NPP), and photosynthetic active radiation (PAR) measured at
each harvest bed during the summer months (June, July, and August) of 2000. In the northern and central region, the agar yield
was 35% to 37% (Bahía Todos Santos, El Rosario, Isla de Cedros, and Islas San Benito), whereas lower yields were obtained
from the southern beds (Punta Eugenia and Bahía Asunción). In contrast, the agar quality increased from the northern to the
southern beds. A lower gel strength was obtained from Bahía Todos Santos and El Rosario (268 ± 16 and 205 ± 5 gcm−2) with a higher gel strength obtained from Isla de Cedros, Islas San Benito, and Bahía Asunción (384 to 444 ± 25 gcm−2). Yield was not correlated with the bryozoan content but was inversely correlated with the protein content in the seaweed.
The sulfate content in the agar was inversely correlated with the gel strength and with the melting temperature. The 3,6-anhydrogalactose
content showed slight variations among harvested beds. Analysis of satellite-derived data showed an equatorward increase of
the SST, NPP, and PAR. The agar content correlated inversely with the equatorward increase of the NPP, whereas agar quality,
i.e., gel strength, correlated positively with the NPP and PAR. No significant effects were observed on the yield and quality
of agar with the latitudinal change of the SST. 相似文献
20.
Identification and characterization of fermentation inhibitors formed during hydrothermal treatment and following SSF of wheat straw 总被引:1,自引:0,他引:1
Mette Hedegaard Thomsen Anders Thygesen Anne Belinda Thomsen 《Applied microbiology and biotechnology》2009,83(3):447-455
A pilot plant for hydrothermal treatment of wheat straw was compared in reactor systems of two steps (first, 80°C; second,
190–205°C) and of three steps (first, 80°C; second, 170–180°C; third, 195°C). Fermentation (SSF) with Sacharomyces cerevisiae of the pretreated fibers and hydrolysate from the two-step system gave higher ethanol yield (64–75%) than that obtained from
the three-step system (61–65%), due to higher enzymatic cellulose convertibility. At the optimal conditions (two steps, 195°C
for 6 min), 69% of available C6-sugar could be fermented into ethanol with a high hemicellulose recovery (65%). The concentration
of furfural obtained during the pretreatment process increased versus temperature from 50 mg/l at 190°C to 1,200 mg/l at 205°C
as a result of xylose degradation. S. cerevisiae detoxified the hydrolysates by degradation of several toxic compounds such as 90–99% furfural and 80–100% phenolic aldehydes,
which extended the lag phase to 5 h. Acetic acid concentration increased by 0.2–1 g/l during enzymatic hydrolysis and 0–3.4 g/l
during fermentation due to hydrolysis of acetyl groups and minor xylose degradation. Formic acid concentration increased by
0.5–1.5 g/l probably due to degradation of furfural. Phenolic aldehydes were oxidized to the corresponding acids during fermentation
reducing the inhibition level. 相似文献