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1.
In this work, the potential of microwave-assisted alkali pretreatment in order to improve the rupture of the recalcitrant
structures of the cashew able bagasse (CAB), lignocellulosic by-product in Brazil with no commercial value, is obtained from
cashew apple process to juice production, was studied. First, biomass composition of CAB was determined, and the percentage
of glucan and lignin was 20.54 ± 0.70% and 33.80 ± 1.30%, respectively. CAB content in terms of cellulose, hemicelluloses,
and lignin, 19.21 ± 0.35%, 12.05 ± 0.37%, and 38.11 ± 0.08%, respectively, was also determined. Results showed that, after
enzymatic hydrolysis, alkali concentration exerted influence on glucose formation, after pretreatment with 0.2 and 1.0 mo L −1 of NaOH (372 ± 12 and 355 ± 37 mg g glucan−1) when 2% ( w/ v) of cashew apple bagasse pretreated by microwave-assisted alkali pretreatment (CAB-M) was used. On the other hand, pretreatment
time (15–30 min) and microwave power (600–900 W) exerted no significant effect on hydrolysis. On enzymatic hydrolysis step,
improvement on solid percentage (16% w/ v) and enzyme load (30 FPU g CAB-M−1) increased glucose concentration to 15 g L −1. The fermentation of the hydrolyzate by Saccharomyces cerevesiae resulted in ethanol concentration and productivity of 5.6 g L −1 and 1.41 g L −1 h −1, respectively. 相似文献
2.
The influence of ethanol on fermentation by Pachysolen tannophilus was studied. When xylose utilization rate was 80%, ethanol concentration began to decline. Fermentation of P. tannophilus was affected by ethanol addition in the beginning of fermentation; average xylose consumption rate was 0.065 g·l −1·h −1, and maximum specific growth rate was 0.07 h −1 at 28 g·l −1 ethanol, comparing with the average xylose consumption rate of 0.38 g·l −1·h −1 and maximum specific growth rate of 0.14 h −1 in fermentation with no ethanol addition; P. tannophilus stopped growth at 40 g·l −1 ethanol. When the initial ethanol concentration was 30 g·l −1, the addition of glucose in xylose media made the growth of P. tannophilus better, and the most favorable glucose concentration was 15 g·l −1 with the highest biomass of 1.51 g·l −1 as compared with that of 0.95 g·l −1 in pure xylose media. 相似文献
3.
Considering bioethanol production, extensive research has been performed to decrease inhibitors produced during pretreatments, to diminish energy input, and to decrease costs. In this study, sugarcane bagasse was pretreated with NaOH, H2SO4, and water. The higher concentration of phenols, 3.3 g/L, was observed in biomass liquid fraction after alkaline pretreatment. Acid pretreatment was responsible to release considerable acetic acid concentration, 2.3 g/L, while water-based pretreatment was the only to release formic acid, 0.02 g/L. Furans derivatives were not detected in liquid fractions regardless of pretreatment. Furthermore, washing step removed most of the phenols from pretreated sugarcane bagasse. Saccharification of alkali-pretreated biomass plus polyethylene glycol (PEG) at 0.4% (w/v) enhanced 8 and 26% the glucose and the xylose release, respectively, while polyvinylpyrrolidone (PVP) also at 0.4% (w/v) increased the release by 10 and 31% of these sugars, respectively, even without washing and filtration steps. Moreover, these polymers cause above 50% activation of endoglucanase and xylanase activities which are crucial for biomass hydrolysis. 相似文献
4.
The results of this study indicate that an increase in CO 2 percentage to 30% can enhance Scenedesmus sp. growth in autotrophic cultivation to a maximum of 0.85 g/l as compared with 0.6 g/l obtained in the batch with air (after
6 days of cultivation). However, while the CO 2 was higher than 30%, it showed a negative impact on cell growth. A mixotrophic cultivation with 3 g/l of glycerol can achieve
0.38 g l −1 day −1 of the maximum biomass productivity compared with that of 0.21 g l −1 day −1 in autotrophic cultivation. Nevertheless, the lutein content of the mixotrophic cultivation was 0.08–0.1% lower than 0.2–0.25%
obtained in autotrophic cultivation, which led to a lower lutein productivity of 0.36 mg l −1 day −1 in the mixotrophic batch compared with 0.44 mg l −1 day −1 obtained in the autotrophic batch. The limitation of cell growth in the mixotrophic cultivation would be the contributing
factor regarding the lower lutein productivity. The mixotrophic cultivation of repeated batch to remove potential inhibitive
metabolic products from glycerol catabolism does not show an obvious improvement on biomass. Conclusively, mixotrophic cultivation
achieves higher biomass productivity with lower lutein content than that of autotrophic cultivation, which leads to lower
lutein productivity. Therefore, the autotrophic cultivation is preferred in the lutein production. 相似文献
5.
Iodine determination in food samples was performed by inductively coupled plasma mass spectrometry (ICP-MS) after digestion
by microwave-induced combustion (MIC). Sample masses up to 500 mg of bovine liver, corn starch, milk powder, or wheat flour
were completely combusted using the MIC system. Ammonium nitrate (6 mol l −1 solution, 50 μl) was used as an aid for ignition and vessels were charged with 15 bar of O 2. The use of H 2O, 0.9 mmol l −1 H 2O 2, 10 to 50 mmol l −1 (NH 4) 2CO 3 and 56 mmol l −1 tetramethylammonium hydroxide was investigated as absorbing solutions, as well as the suitability of performing a reflux
step after the combustion process. Digestion of food samples by pressurized microwave-assisted acid digestion, microwave-assisted
extraction and conventional extraction of iodine in alkaline solution were also evaluated. Iodine recoveries higher than 99%
were obtained using MIC and 50 mmol l −1 (NH 4) 2CO 3 or 56 mmol l −1 tetramethylammonium hydroxide as absorbing solution and with 5 min for the reflux step. Accuracy was evaluated using certified
reference materials (bovine muscle, corn bran, and milk powder) and agreement better than 97% was obtained. The limit of quantification
by MIC and further ICP-MS determination was 0.002 μg g −1. Blanks were always low and no memory effects were observed. Digestion by MIC allowed the processing of up to eight samples
by each run in 25 min with high efficiency of digestion (residual carbon content lower than 1%) providing a suitable medium
for further iodine determination by ICP-MS. 相似文献
6.
In this paper, two new strians, Issatchenkia occidentalis (Lj-3, CCTCC M 2006097) and Issatchenkia orienalis (S-7, CCTCC M 2006098), isolated from different environments on solid media, were used in the detoxification process of the
hemicellulosic hydrolysate of sugarcane bagasse. High-pressure liquid chromatography elution curve of UV-absorption compounds
represented by acetic acid, furfural, and guaiacol (toxic compounds found in the hemicellulosic hydrolysate) showed that several
chromatographic peaks were evidently diminished for the case of detoxified hydrolysate with isolate strains compared to the
high peaks resulted for no detoxified hydrolysate. It was clear that these inhibitors were degraded by the two new isolates
during their cultivation process. Fermentation results for the biodetoxified hydrolysate showed an increase in xylitol productivity
( Q
p) by 1.97 and 1.95 times (2.03 and 2.01 g l −1 h −1) and in xylitol yield ( Y
p) by 1.72 and 1.65 times (0.93 and 0.89 g xylitol per gram xylose) for hydrolysate treated with S-7 and Lj-3, respectively,
in comparison with no detoxified hydrolysate (1.03 g l −1 h −1 and 0.54 g xylitol per gram xylose). This present work demonstrated the importance of Issatchenkia yeast in providing an effective biological detoxification approach to remove inhibitors and improve hydrolysate fermentability,
leading to a high xylitol productivity and yield. 相似文献
7.
Pretreatment procedures of sugarcane bagasse with lime (calcium hydroxide) or alkaline hydrogen peroxide were evaluated and
compared. Analyses were performed using 2 3 factorial designs, with pretreatment time, temperature, and lime loading and hydrogen peroxide concentration as factors.
The responses evaluated were the yield of total reducing sugars (TRS) and glucose released from pretreated bagasse after enzymatic
hydrolysis. Experiments were performed using the bagasse, as it comes from an alcohol/sugar factory and bagasse, in the size,
range from 0.248 to 1.397 mm (12–60 mesh). The results show that, when hexoses and pentoses are of interest, lime should be
the pretreatment agent chosen, as high TRS yields are obtained for non-screened bagasse using 0.40 g lime/g dry biomass at
70 °C for 36 h. When the product of interest is glucose, the best results were obtained with lime pretreatment of screened
bagasse. However, the results for alkaline peroxide and lime pretreatments of non-screened bagasse are not very different. 相似文献
8.
There is a lack of fundamental knowledge about the scale up of biosurfactant production. In order to develop suitable technology
of commercialization, carrying out tests in shake flasks and bioreactors was essential. A reactor with integrated foam collector
was designed for biosurfactant production using Bacillus subtilis isolated from agricultural soil. The yield of biosurfactant on biomass ( Y
p/x), biosurfactant on sucrose ( Y
p/s), and the volumetric production rate ( Y) for shake flask were obtained about 0.45 g g −1, 0.18 g g −1, and 0.03 g l −1 h −1, respectively. The best condition for bioreactor was 300 rpm and 1.5 vvm, giving Y
x/s, Y
p/x, Y
p/s, and Y of 0.42 g g −1, 0.595 g g −1, 0.25 g g −1, and 0.057 g l −1 h −1, respectively. The biosurfactant maximum production, 2.5 g l −1, was reached in 44 h of growth, which was 28% better than the shake flask. The obtained volumetric oxygen transfer coefficient
( K
L
a) values at optimum conditions in the shake flask and the bioreactor were found to be around 0.01 and 0.0117 s −1, respectively. Comparison of K
L
a values at optimum conditions shows that biosurfactant production scaling up from shake flask to bioreactor can be done with
K
L
a as scale up criterion very accurately. Nearly 8% of original oil in place was recovered using this biosurfactant after water
flooding in the sand pack. 相似文献
9.
The effect of pH and associated ionic strength on the primary yields in the radiolysis of pressurised water has been assessed
by diffusion-kinetic calculations for temperatures in the range 100–300°C. Account has been taken for ionic strength I up to 0.1 mol kg −1, assuming that the counter ions of H + in acid solutions and of OH − in base solutions have unit charge. In acid solutions, the H + ions react with e −
aq. The decrease in G(e −
aq) and the increase in G(H) with decreasing pH becomes substantial for [H +] ≥ 1 × 10 −4 m, but the primary yields of oxidising species are almost constant. In alkaline solutions, the OH − anions affect the spur chemistry of radiation-generated protons and hydroxyl radicals for [OH −] ≥ 1 × 10 −4 m. The scavenging of H atoms and hydrogen peroxide becomes significant for [OH −] ≥ 1 × 10 −2 m. The total yields G(OH) + G(O −) and G(H 2O 2) + G(HO 2
−) are independent of base concentration below 0.01 m. In more alkaline solutions, G(OH) + G(O −) increases, whereas G(H 2O 2) + G(HO 2
−) decreases with increasing [OH −]. Calculations showed the substantial yield of the reaction O − + e −
aq in 0.1 m base solution. Spur chemistry in alkaline hydrogenated water is not affected by the presence of H 2 if less than 0.001 m of hydrogen is added. 相似文献
10.
Pseudomonas aeruginosa strain OBP1, isolated from petroleum sludge, was used to produce biosurfactant from a modified mineral salt medium with 2%
n-hexadecane as sole source of carbon. The crude biosurfactant was fractionated using TLC and HPLC. Using FTIR spectroscopy,
1H NMR, and LC-MS analyses, the chemical structure of the purified fraction of crude biosurfactant was identified as rhamnolipid
species. The LC-MS spectra show that monorhamnolipid ( l-rhamnopyranosyl-β-hydroxydecanoyl-β- hydroxydecanoate, Rha-C 10-C 10) was produced in abundance with the predominant congener [M–H] − ions for l-rhamnopyranosyl- l-rhamnopyranosyl-3-hydroxydecanoyl-3-hydroxydecanoate (Rha-Rha-C 10-C 10). Seven different carbon substrates and five nitrogen sources were examined for their effect on rhamnolipid production. Using
n-hexadecane (20 g/l) as carbon substrate and urea along with (NH 4) 2SO 4 (2 g/l each) as nitrogen source was found to be the best, with a maximum yield of 4.8 g/l. The biosurfactant reduced the
surface tension of water to 31.1 mNm −1 with a critical micelle concentration of 45 mg/l. The biosurfactant showed a better emulsifying activity against a variety
of hydrocarbon and achieved a maximum emulsion index of 82% for diesel. The purified biosurfactant showed a significant antibacterial
activity against Staphylococcus aureus at a minimum inhibitory concentration of 8 μg/ml. 相似文献
11.
The protonation and deprotonation of the Nb 2O 5 surface has been followed in order to understand the reactions of surface of this catalyst. The simultaneous potentiometric
and conductometric titrations had been carried by using 50 mL of water suspension of Nb 2O 5 40 g L −1. The oxide was entirely deprotonated when adding 0.4 mL NaOH 1 mol L −1, and later titrated with 0.1 mol L −1. The titration had supplied K
1 and K
2 and the obtained values were 3.24 × 10 −3 and 4.17 × 10 −8, respectively. The zero point charge was pH pcz = 4.94. The thermodynamic studies were carried out by using 50 mL of a 40 g/L Nb 2O 5 aqueous suspension with the pH adjusted to pH PZC value. The suspension was titrated with 0.5 mol/L of HNO 3 or NaOH for protonation or deprotonation studies, respectively, in an isoperibol calorimeter CSC ISC-4300. Thus, the obtained
thermodynamic values of the protonation and deprotonation of Nb 2O 5 were Δ dp
G = −37.60 kJ/mol, Δ dp
H = −23.72 kJ/mol and Δ dpS = 47 J/(mol K). 相似文献
12.
In this study, an efficient procedure was developed for callus induction and regeneration of kiwifruit ( Actinidia deliciosa) using different organs of shoots developed under in vitro conditions. Effects of explants source and media (M 1, 1.0 mg l −1 BA + 2.0 mg l −1 2,4-D–M 2, 1.0 mg l −1 NAA + 2.0 mg l −1 2,4-D) on initiation of callus were examined in order to obtain callus for organogenesis. The best callus for plant regeneration
was obtained from leaf explants on Murashige and Skoog’s medium (MS) supplemented with M 2. Formation of callus from leaf of kiwifruit ( A. deliciosa) was cultured in MS medium containing different concentration of N 6-benzylaminopurin (BA; 0.0, 1.0, 2.0, 4.0, 6.0, 8.0 mg l −1) for callus proliferation and plant regeneration. Although the first shoot formation was appeared in medium containing 6.0
and 8.0 mg l −1 BA, the best shoots formation was obtained in medium with 4.0 mg l −1 BA. 相似文献
13.
Aloe vera L., a member of Liliaceae, is a medicinal plant and has a number of curative properties. We describe here the development
of tissue culture method for high-frequency plantlet regeneration from inflorescence axis-derived callus cultures of sweet
aloe genotype. Competent callus cultures were established on 0.8% agar-gelled Murashige and Skoog’s (MS) basal medium supplemented
with 6.0 mg l −1 of 2,4-dichlorophenoxyacetic acid (2,4-D) and 100.0 mg l −1 of activated charcoal and additives (100 mg l −1 of ascorbic acid, 50.0 mg l −1 each of citric acid and polyvinylpyrrolidone, and 25.0 mg l −1 each of l-arginine and adenine sulfate). The callus cultures were cultured on MS medium containing 1.5 mg l −1 of 2,4-D, 0.25 mg l −1 of Kinetin (Kin), and additives with 4% carbohydrate source for multiplication and long-term maintenance of regenerative
callus cultures. Callus cultures organized, differentiated, and produced globular embryogenic structures on MS medium with
1.0 mg l −1 of 2,4-D, 0.25 mg l −1 of Kin, and additives (50.0 mg l −1 of ascorbic acid and 25.0 mg l −1 each of citric acid, l-arginine, and adenine sulfate). These globular structures subsequently produced shoot buds and then complete plantlets on
MS medium containing 1.0 mg l −1 of 6-benzylaminopurine and additives. A hundred percent regenerated plantlets were hardened in the greenhouse and stored
under an agro-net house/nursery. The regeneration system defined could be a useful tool not only for mass-scale propagation
of selected genotype of A. vera, but also for genetic improvement of plant species through genetic transformation. 相似文献
14.
A feeding technology that was suitable for improving the nisin production by Lactococcus lactis subsp . lactis W28 was established. The effects of initial sucrose concentration (ISC) in the fermentation broth, feeding time, and feeding
rate on the fermentation were studied. It was observed that a fed-batch culture (ISC = 10 g l −1) with 100 ml sucrose solution (190 g l −1) being evenly fed (9–10 ml h −1) into the fermenter after 3-h fermentation gave the best performance in terms of biomass and nisin yield. Under these conditions,
the total biomass and the total nisin yield were approximately 23% and 51% higher than those in batch fermentation, respectively.
When the sucrose concentration was controlled at 5–10 g l −1 in variable volume intermittent fed-batch fermentation (VVIF) with ISC = 10 g l −1, the total biomass and the total nisin yield were 29% and 60% above those in batch fermentation, respectively. The VVIF proved
to be effective to eliminate the substrate inhibition by maintaining sucrose at appropriate levels. It is also easy to be
scaled up, since various parameters involved in industrial production were taken into account. 相似文献
15.
The inclusion complexes induced by cyclodextrins and its derivates have been shown previously to enhance the biotransformation
of hydrophobic compounds. Using hydroxypropyl-β-cyclodextrin (HP-β-CD; 20% w/ v), the water solubility of cortisone acetate increased from 0.039 to 7.382 g L −1 at 32 °C. The solubilization effect of HP-β-CD was far superior to dimethylformamide (DMF) and ethanol. The dissolution rate
also significantly increased in the presence of HP-β-CD. The enzymatic stability of Δ 1-dehydrogenase from Arthrobacter simplex TCCC 11037 was not influenced by the increasing concentrations of HP-β-CD contrary to the organic cosolvents which negatively
influenced in the order DMF > ethanol. The activity inhibition effect caused by HP-β-CD was not so conspicuous as ethanol
and DMF. Inactivation constants of ethanol, DMF, and HP-β-CD were 5.832, 4.541, and 1.216, respectively. The inactivation
energy ( E
a) was in the order of HP-β-CD (55.1 kJ mol −1) > ethanol (39.9 kJ mol −1) > DMF (37.1 kJ mol −1). 相似文献
16.
The photocatalytic properties of nanocrystalline TS-1 were confirmed via the degradation of an aqueous solution of the model
compound methyl orange (MO). The light intensity and quantum yield were measured by ferrioxalate actinometry and the values
are 1.7 × 10 −5 einstein l −1 s −1 and 0.71, respectively. The experimental parameters such as catalyst loading, pH and initial concentration of MO were optimized
at 1.5 g/L, 10 and 300 μM, in order. The results showed that the dye molecules are completely degraded to CO 2, H 2O and simple inorganic ions. 相似文献
17.
In this study, a fermentor consisting of four linked stirred towers that can be used for simultaneous saccharification and
fermentation (SSF) and for the accumulation of cell mass was applied to the continuous production of ethanol using cassava
as the starchy material. For the continuous process with SSF, the pretreated cassava liquor and saccharification enzyme at
total sugar concentrations of 175 g/L and 195 g/L were continuously fed to the fermentor with dilution rates of 0.014, 0.021,
0.031, 0.042, and 0.05 h −1. Considering the maximum saccharification time, the highest volumetric productivity and ethanol yield were observed at a
dilution rate of 0.042 h −1. At dilution rates in the range of 0.014 h −1 to 0.042 h −1, high production rates were observed, and the yeast in the first to fourth fermentor showed long-term stability for 2 months
with good performance. Under the optimal culture conditions with a feed sugar concentration of 195 g/L and dilution rate of
0.042 h −1, the ethanol volumetric productivity and ethanol yield were 3.58 g/L∙h and 86.2%, respectively. The cell concentrations in
the first to fourth stirred tower fermentors were 74.3, 71.5, 71.2, and 70.1 g dry cell/L, respectively. The self-flocculating
yeast, Saccharomyces cerevisiae CHFY0321, developed by our group showed excellent fermentation results under continuous ethanol production. 相似文献
18.
In the present study, a novel oleaginous Thraustochytrid containing a high content of docosahexaenoic acid (DHA) was isolated
from a mangrove ecosystem in Malaysia. The strain identified as an Aurantiochytrium sp. by 18S rRNA sequencing and named KRS101 used various carbon and nitrogen sources, indicating metabolic versatility. Optimal
culture conditions, thus maximizing cell growth, and high levels of lipid and DHA production, were attained using glucose
(60 g l −1) as carbon source, corn steep solid (10 g l −1) as nitrogen source, and sea salt (15 g l −1). The highest biomass, lipid, and DHA production of KRS101 upon fed-batch fermentation were 50.2 g l −1 (16.7 g l −1 day −1), 21.8 g l −1 (44% DCW), and 8.8 g l −1 (40% TFA), respectively. Similar values were obtained when a cheap substrate like molasses, rather than glucose, was used
as the carbon source (DCW of 52.44 g l −1, lipid and DHA levels of 20.2 and 8.83 g l −1, respectively), indicating that production of microbial oils containing high levels of DHA can be produced economically when
the novel strain is used. 相似文献
19.
The kinetics of hexacyanoferrate(III) reduction by hydrogen peroxide in strongly alkaline media leading to hexacyanoferrate(II)
ion have been studied spectrophotometrically within the wavelength range 300–500 nm. The reaction obeys a simple pseudo-first-order
rate expression under the applied conditions, namely, a large excess of the reductant and OH − anion concentrations, and a low oxidant concentration. The linear dependences of the pseudo-first-order rate constant on
OH − and H 2O 2 concentrations are consistent with the rate law of the form: where and are the second- and the pseudo-third-order rate constants for the electron transfer from HO 2
− and O 2
2− to [Fe(CN) 6] 3−, respectively. The apparent activation parameters determined at 0.4 M NaOH are as follows: Δ H
# = (18.0 ± 1.0) kJ mol −1 and Δ S
# = (−155 ± 3.5) J K −1 mol −1. The possible mechanism of the reaction is discussed. 相似文献
20.
The corrosion inhibition of X-70 pipeline steel in saltwater saturated with CO 2 at 50 °C with carboxyamido imidazoline has been evaluated by using electrochemical techniques. Techniques included polarization
curves, linear polarization resistance, electrochemical impedance, and electrochemical noise measurements. Inhibitor concentrations
were 0, 1.6 × 10 −5, 3.32 × 10 −5, 8.1 × 10 −5, 1.6 × 10 −4, and 3.32 × 10 −4 mol l −1. All techniques showed that the best corrosion inhibition was obtained by adding 8.1 × 10 −5 mol l −1 of carboxyamido imidazoline. For inhibitor concentrations higher than 8.1 × 10 −5 mol l −1 a desorption process occurs, and an explanation has been given for this phenomenon. 相似文献
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