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1.
Summary Root-colonizing pseudomonads capable of inhibiting seedling winter wheat (Triticum aestivum L.) root growth in an agar seedling bioassay also significantly inhibited wheat root growth in vermiculite; however, the inhibitory trait is quite labile in laboratory culturing. The extent of inhibition in both the agar and vermiculite medium depended on inoculum level. These pseudomonads were found to produce a toxin capable of inhibiting growth ofEscherichia coli C-la andBacillus subtilis. Field isolates that strongly inhibit growth of indicator bacteria also inhibited root growth. Toxin production by the bacteria appeared necessary for inhibition of root growth and indicator bacteria as toxin-negative (TOX–) mutants no longer inhibited either. Antibiosis towardsE. coli as well as wheat seedling root inhibition in agar was reversed by L-methionine, providing further evidence that a toxin, produced by these organisms, is involved in growth retardation.Contribution in cooperation with the College of Agric. Res. Center, Washington State Univ., Pullman, WA 99164. Scientific Paper No. 6837. 相似文献
2.
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
3.
The in vivo metabolism of indole-3-acetic acid (IAA) in etiolated hypocotyls of lupin (Lupinus albus L., from Bari, Italy) was investigated by appliying IAA labelled with two radioisotopes ([1-14C]-IAA+[5-3H]-IAA) to the apical end of decapitated seedlings, followed by extraction of the radioactivity in the different regions along the hypocotyl. This method allowed detection of IAA decarboxylation in zones distant from the cut surface and, therefore, containing intact cells. When IAA was added directly in solution to the cut surface, decarboxylation was high especially in those hypocotyl regions where transient accumulations characteristic of the polar transport of IAA occurred. In 10-day-old seedlings such accumulations were observed both in the elongation zone (2nd, 3rd, and 4th cm) and in the non elongating basal zone (8th, 9th and 10th cm). When the IAA, instead, was applied with an agar block deposited on the cut surface, IAA metabolism (decarboxylation as well as conjugation) was increased but almost exclusively in tissues within 10 mm of the cut surface. In both kinds of experiment, the increase in IAA decarboxylation seemed to coincide with a decrease in the transport of IAA, since in the assay without agar the transient accumulations of radioactivity were probably due to a decrease in the transport velocity, while in the assay with agar the transport intensity was much lower than in the assay without agar. These results point to a competitive relationship between IAA metabolism and transport. Consequently, it is suggested that hypocotyl regions that probably use auxin for development processes (e.g., cell elongation and differentiation) may have a more intense IAA metabolism in parallel with their higher IAA concentrations. 相似文献
4.
Three gracilarioid species, Gracilariopsis bailiniae and Gracilaria tenuistipitata from Vietnam and Gracilaria gracilis from Russia, were studied in order to determine whether Gracilaria gracilis might be a superior species for cultivation in brackish-water ponds for agar production compared with the Vietnamese species.
The effects of different salinity levels on the growth rate and agar production as well as agar properties of three gracilarioid
species were compared in controlled laboratory experiments. Gracilaria tenuistipitata and G. gracilis were tolerant to low salinity (∼10‰), whereas Gp. bailiniae died under these conditions. G. tenuistipitata showed superior growth among the three species examined. Gracilaria gracilis had the highest agar content [36.8–46.6% dry weight (dw)]. Agar yield from Vietnamese gracilarioids did not exceed 30% dw.
Gel strength of native agar from Gracilaria gracilis was two-fold higher that from Vietnamese species (278 g cm−2 vs 130 g cm−2). Alkali pretreatment increased gel strength significantly for Gracilaria gracilis (1.4-fold), and G. tenuistipitata and Gp. bailiniae (2.3-fold) compared with native agar. The results suggest that Gracilaria gracilis may be a suitable species for production of reasonably good quality agar. 相似文献
5.
The chemical and gelling properties of agar from G. verrucosa collected from Izmit bay in Turkey at different months of the year were studied. Purification of agar was performed by using amylase treatment and isopropyl alcohol precipitation. The phycocolloid content was between 24.0–43.0% of the algal dry weight and was maximum in summer collected algae. Relative total sulfate and 3,6-anhydrogalactose content in the agar were determined from the ratios of infrared spectroscopy band intensities at 1250/2920 cm–1 and 930/2920 cm–1, respectively. 3,6-anhydrogalactose and sulfate contents were the highest in agar from algae collected from June until November and January until July, respectively. The gel strength of native agar were the highest from in autumn collected algae and increased to about 1250 N m–2 after alkali treatment. Thus, this study demonstrated that G. verrucosa from Turkey produces an agar with optimal chemical and gelling properties after alkali-treatment in fall and winter collected algae and may be used for industrial agar production. 相似文献
6.
T. D. Pickering V. H. Sladden R. H. Furneaux J. A. Hemmingson P. Redfearn 《Journal of applied phycology》1993,5(1):85-91
Plant growth rates and agar characteristics were compared for two agarophytes,Gracilaria chilensis (Gracilariales, Rhodophyta) andG. truncata, so that the suitability ofG. truncata for mariculture could be assessed.G. chilensis plants grew steadily in the laboratory culture system at rates of 5–8% day-1 (mean Relative Growth Rate) throughout the 6 week experimental period, with no decline in health.G. truncata plants grew at rates of 2–4% day-1 for 5 weeks, but during the sixth week their apical tips became necrotic and growth rates fell to zero. There was no significant difference in the dry matter content (as a percentage of their wet weight) between the two species ofGracilaria, with values falling in the range of 16–19%. Slightly higher agar yields were obtained from alkali-treatedG. chilensis (17–20% dry matter) than from untreatedG. truncata (16–18%) although the agar fromG. truncata formed softer gels from which it was more difficult to recover. The gel strength of untreated agar extracted fromG. chilensis was very low (ca. 100 g cm-2 for a 1% gel) but when an alkali treatment step was included in the extraction process, it increased to 520 g cm-2 for a 1% gel. Contrary to an earlier report, untreatedG. truncata agar also had a very low gel strength (ca. 100 g cm-2 for a 1.5% gel), but it rose to only 167 g cm-2 after alkaline treatment. 相似文献
7.
Badji B Mostefaoui A Sabaou N Lebrihi A Mathieu F Seguin E Tillequin F 《Journal of industrial microbiology & biotechnology》2007,34(6):403-412
An actinomycete strain NM94 was isolated from a Saharan soil sample by a dilution agar plating method using chitin-vitamins
B medium supplemented with penicillin. The strain presented the morphological and chemical characteristics of the genus Nonomuraea. On the basis of 16S rDNA analysis and physiological tests, this isolate was found to be quite different from the known species
of Nonomuraea and might be new. The strain NM94 secreted several antibiotics on yeast extract malt extract glucose medium that were active
against some Gram-positive bacteria, yeast, and fungi. The antibiotics were extracted with dichloromethane and detected by
bioautography on silica gel plates using Mucor
ramannianus and Bacillus
subtilis as the test organisms. Among these antibiotics, a complex called 94A showed interesting antifungal activity. It was selected
and purified by reverse-phase HPLC. This complex was composed of five compounds. Spectroscopic studies by infrared, mass,
and 1H NMR of the compounds were carried out. Initial results showed that these molecules differed from the known antibiotics produced
by other Nonomuraea species. 相似文献
8.
Jeffrey Honda Man-Wi Han Norman C. Leppla 《Entomologia Experimentalis et Applicata》1996,81(2):175-180
Ingredient substitutions for agar or carrageenan in artificial diets for lepidopterous larvae were evaluated. A sodium polyacrylamide polyacrylate gelling agent, Water-Lock G-400, was compared with agar for solidifying diets of the cabbage looper, Trichoplusia ni (Hübner), omnivorous looper, Sabulodes aegrotata (Gueneé), and the western avocado leafroller, Amorbia cuneana Walsingham. Water-Lock G-400 is considerably less expensive than agar or carrageenan, it does not require heating to gel, and it is made from a dependable supply of agricultural starch.
Sabulodes aegrotata pupae from larvae reared on agar were significantly heavier than those reared on Water-Lock G-400. However, the remainder of the variables observed (larval survival, developmental times, fecundity, sex ratio and pupal weights for A. cuneana and T. ni) were all independent of diet. Decreasing the total amount of ingredients in a Water-Lock-G-400 diet produced fewer and smaller T. ni pupae than did an agar diet when the larvae were reared using a mass production protocol. However, these lower values were still above acceptable levels for mass production and reduced the cost of diet production by 65%.Further ingredient substitutions impaired larval development (i.e., replacing pinto beans with soy protein or combinations of soy protein and -cellulose), while others did not (i.e., excluding pinto beans and reducing water content and replacing pinto beans with -cellulose or corn cob grits). Moisture control by adding corn cob grits to diets increased the yield of pupae, while removing water from diets increased survivorship and the yield of pupae. 相似文献
9.
Rapid propagation of agave by in vitro tissue culture 总被引:1,自引:0,他引:1
L. T. Binh L. T. Muoi H. T. K. Oanh T. D. Thang D. T. Phong 《Plant Cell, Tissue and Organ Culture》1990,23(1):67-70
A procedure for rapid propagation of Agave (A. cantala Roxb., A. fourcroydes Lem. and A. sisalana Perrine, (Agavaceae) have been developed. The explants were excised from stolon plantlets, sterilized and cultivated on Murashige and Skoog (MS) basal medium containing 2% sucrose, 10% coconut water and 0.8% agar. The addition of following combination of growth substances—0.075 mgl-1 naphthalenacetic acid (NAA)+0.1 mgl-1 indolylbutyric acid (IBA)+0.5 mgl-1 kinetin (KIN) caused an extensive proliferation of multiple shoot primordia. Subcultures of these on the same medium were successful for the multiplication with an index of 3–4 times per 4 weeks subculture period. Shoots were rooted on hormone free MS medium and then transferred into a sand bed for acclimation before field planting. 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.
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
12.
Chemical structure and quality of agars from Gracilaria 总被引:3,自引:0,他引:3
Erminio Murano 《Journal of applied phycology》1995,7(3):245-254
Agar polymers synthesized by species of the genus Gracilaria constitute a complex mixture of molecules, containing several extremes in structure. Sulphate hemi-esters, methyl ethers
and pyruvic ketals can alter in a number of ways the structural regularity of agar based on strictly 3-O-linked β-l-galactopyranose and 4-O-linked α-l-galactopyranose residues. In comparison with agars from Gelidium and Pterocladia, agars from Gracilaria can have higher degrees of sulphation, methoxylation and pyruvylation. The gelling ability of agars from most of Gracilaria species is considerably improved by adopting, before extraction, an alkali pretreatment which converts α-l-galactose 6 sulphate into 3,6-anhydro-α-l-galactose. Native agars obtained from Gracilaria cannot be classified, with few exceptions, as bacteriological grade agar as they have a high content of methoxyls and consequently
high gelling temperatures. On the contrary, the genus Gracilaria is considered the most important source of food and sugar-reactive grade agars.
Among techniques which can be used to study algal polysaccharides, combined 1H and 13C nuclear magnetic resonance spectroscopy represent the most effective and powerful method for the investigation of the chemical
structure of agarocolloids. 相似文献
13.
菜心组织培养技术初探 总被引:1,自引:1,他引:0
为建立菜心(Brassica campestris ssp.chinensis var.utilis)的快繁技术体系,以花药和子叶-子叶柄为外植体进行组织培养研究。结果表明,花药培养以选取未开放的花蕾为宜,且花柱略高于花瓣,此时小孢子多数处于单核靠边期。菜心花粉的萌发率不高,且秋冬季的花粉比夏季的萌发率高。菜心花药愈伤组织诱导培养基为:MS+1.0 mg L–1 KT+1.0 mg L–1 2,4-D+3%糖+6 g L–1琼脂+8%椰乳,不定芽诱导培养基为:MS+2.0 mg L–1 6-BA+0.5 mg L–1 NAA+1.0 g L–1活性炭+2%糖+6 g L–1琼脂或MS+2.0 mg L–1 ZT+0.5 mg L–1 IAA+0.5 g L–1 AgNO3+1.0 g L–1活性炭+2%糖+6 g L–1琼脂。花药培养的不定芽诱导率为36.7%,不定芽培养出现褐化现象,不能形成再生植株;而以子叶-子叶柄为外植体培养获得的植株再生率可达80%。 相似文献
14.
Agars from Chilean Gelidiaceae 总被引:2,自引:2,他引:0
Cystocarpic, tetrasporic and vegetative thalli of Gelidium chilense were extracted with water at 95 °C. The contents of 3,6-anhydro-galactose and sulfate group of the hydrocolloids correspond to those of an agar-type polysaccharide. The percentages of 6-O-methyl-galactose and of pyruvic acid ranged between 5.7–6.2% and 0.42–0.54%, respectively. The gel melting and gelation temperatures of Gelidium chilense, G. rex and G. lingulatum agars were determined. A correlation between 6-O-methylgalactose content and gelation temperatures was not observed. It was found by anion-exchange chromatography that 19.8% of tetrasporic and 4.9% of vegetative G. chilense agars are unsulfated polymers. Structural studies on the neutral fraction from tetrasporic G. chilense agar by partial hydrolysis and 1H NMR spectroscopy have shown that it is mainly composed of agarose. Methylation analysis, oxidative hydrolysis and partial hydrolysis, followed by 1H NMR spectroscopy, have shown that the neutral fraction of the agar from tetrasporic Gelidium rex is agarose. The results obtained in this work are compared with previously reported data on studies of agars from Chilean Gelidium species. 相似文献
15.
Dana L. Richter Sara C. Robinson Maria P. Beardslee Maureen L. Habarth 《Mycological Research》2008,112(6):717-724
Forty species of fungi, representing a range of ecological and taxonomic groups, were tested for their ability to grow on agar media amended with lithium chloride (LiCl) at 1.5, 3 and 6 g l−1. Species of Trichoderma varied considerably in their sensitivity to LiCl; at one week on 6 g l−1 LiCl medium, the growth of seven species of Trichoderma was considerably inhibited; however, by three weeks at this level, four of the species tested were able to attain ≥30 % of control growth. Of the seven species tested, an isolate of T. viride was the most sensitive to LiCl in agar. Eleven other imperfect fungi also showed a range of ability to grow on agar amended with LiCl, from total inhibition to complete lack of inhibition. Six ascomycete fungi were greatly inhibited by LiCl at all levels; however, an isolate of Chaetomium globosum was highly tolerant of LiCl. Seven basidiomycete wood-decay fungi were quite sensitive to LiCl in agar, showing total to nearly total inhibition even at the lowest level; however, after three weeks, an isolate of Postia placenta was nearly uninhibited except at 6 g l−1. Five ectomycorrhizal basidiomycete fungi were totally inhibited by all levels of LiCl; however, one ectomycorrhizal imperfect fungus (Cenococcum graniforme) was able to grow at 3 g l−1 and was uninhibited at 1.5 g l−1. Four zygomycete fungus isolates were nearly unaffected in their growth by all levels of LiCl. 相似文献
16.
The agarophyte, Gracilaria verrucosa Strain G-16, has been grown in sustained cultivation over a period of five years. During this period, a number of experiments were conducted to examine the productivity, agar yield and agar gel strength of this strain. Productivities range from 3–31 g dry wt m–2 d–1 and are generally highest in the summer when annual water temperatures and daily irradiances are highest. In the summer months agar yield from Strain G-16 appears to be lowest whereas the gel strength of the agars was highest (> 750 g cm–2). 相似文献
17.
Pratt RG 《Mycopathologia》2006,162(2):133-140
Nine species of Bipolaris, Curvularia, Drechslera, and Exserohilum were compared for sporulation on agar media and for enhancement of sporulation by growth on four cellulose-containing substrates
(index card, filter paper, cheesecloth, cotton fabric). On two natural and one synthetic agar media, sporulation varied from
profuse to nonexistent among three isolates of each species. Growth of all species on cellulose substrates resulted in large
and significant increases in sporulation. Growth on index card pieces often provided the greatest increases, but no single
substrate was superior for all species, and significant substrate × isolate interactions were observed within species. Overlay
of filter paper onto whole colonies in agar plates resulted in 2 to 18-fold increases in sporulation for eight of nine species
and production of spores in sufficient quantity for most experimental purposes. Overlay of soil dilution plates with filter
paper to promote sporulation of colonies enabled detection of B. spicifera, B. hawaiiensis, C. lunata, and E. rostratum at relatively low population levels (≤1.3 × 103 colony-forming units per gram of soil) in samples of a naturally infested soil. Results indicate that enhancement of sporulation
by growth of species of Bipolaris, Curvularia, Drechslera, and Exserohilum on cellulose substrates may facilitate (i) their identification in culture, (ii) production of spores at relatively high
concentrations, and (iii) detection and enumeration of these fungi in soil. 相似文献
18.
Self-transmissible plasmids carryinghis andnif genes fromKlebsiella pneumoniae have been introduced into threehis mutants ofProteus mirabilis: strains 5006-1, WR19 and WR20. Expression ofhis by the transconjugants was unequivocal, if slightly temperature-sensitive, but none was Nif+ when tested for acetylene reduction in anaerobic glucose medium using inocula from rich or glucose-minimal aerobic agar cultures. Succinate or pyruvate in place of glucose, low glucose, lower temperature or elevated Na2MoO4 did not allownif expression and no nitrogenase MoFe-protein peptide was detected immunologically after exposure to conditions in which diazotrophic enterobacteria, normal or genetically constructed, derepressnif.One strain,P. mirabilis WR19, carrying thehis nif Kmr plasmid pMF250 was examined in detail. Thenif activator genenifA was introduced on the plasmid pCK1. Such derivatives remained Nif- when tested, after aerobic growth on rich agar media, with normal or low glucose, with succinate or with elevated Mo. However, pre-conditioning by aerobic growth on glucose-minimal agar led to subsequent anaerobic expression ofnif in glucose medium from pMF250 in WR19 carrying pCK1. NH
4
+
or proline could serve as N-source in the glucose-minimal agar. Maximum activity was about 5% of that ofK. pneumoniae in our assay conditions. Material cross-reacting with anti-serum to the nitrogenase MoFe protein was formed. Nitrogenase activity was not switched off by NH
4
+
.P. mirabilis WR19 (pCK1) showed NH
4
+
-constitutive temperature-sensitive kanamycin resistance (anif-related phenotype of this plasmid) in aerobic glucose minimal medium. Expression ofnif inP. mirabilis WR19 (pCK1, pMF250) was NH
4
+
-repressible despite the constitutivenifA character of pCK1 and introduction of thentrA
+ plasmid pMM17 did not alter this phenotype. However, pCK1 did not give rise to NH
4
+
-constitutive diazotrophy in the wild-typeK. pneumoniae M5al. A construct of WR19 carrying pMF250 and constitutiventrC plasmid (pMD45) remained Nif- even after pre-growth on glucose-minimal media.We conclude (a) thatP. mirabilis forms a gene product functionally equivalent to that ofntrA inK. pneumoniae, (b) that it forms no functional equivalent of thentrC product in our growth conditions. The need for pre-conditioning on aerobic glucose media remains perplexing.Non-common abbreviation NFDM
Nitrogen-free-Davis-Mingioli medium 相似文献
19.
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
20.
Yolanda Freile-Pelegrín 《Journal of applied phycology》2000,12(2):153-158
The agar yield and quality characteristics of Gracilaria cornea from Yucatán, Mexico, werestudied during 18 months of storage. Biomass wasstored at a temperature of 22.1 ± 0.9 °Cand humidity of 59.8±3.6%. The agar contentvaried erratically, but the average value waspractically constant over the storage period with an average of 20.1 ± 1.5±. Gel strength, gelling and meltingtemperatures were negatively affected by the totalstorage time. No significant changes were found duringthe first five months for these characteristics withmean values of 1134 ± 57 g cm-2, 40.8 ±0.4 °C and 91.2 ± 0.9 °Crespectively. Agar degradation was evident after thefifth month and accounted for a 17± loss in gelstrength and 7± in gelling and meltingtemperatures. Nevertheless, gel strength valuesremained around 930 ± 23 g cm-2 with nosignificant changes until the end of the storageperiod. The decrease in gel strength showed asignificant relationship with decrease in3,6-anhydrogalactose but not variation in sulphatecontent. This was probably due to agar hydrolysiscaused by enzymatic processes of endogenous and/ormicrobial origin. These results suggest that thetropical G. cornea had a similar resistance todegradation during storage to that observed for G. chilensis, a cold water species. Agar qualityand yield in G. cornea after one and a half yearof storage are within the range of food grade agar. 相似文献