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1.
Enzymatic saccharification and fermentation of xylose-optimized dilute acid-treated lignocellulosics
Yun-Chin Chung Alan Bakalinsky Michael H. Penner 《Applied biochemistry and biotechnology》2005,124(1-3):947-961
The cellulose reactivity of two lignocellulosic feedstocks, switchgrass and poplar, was evaluated under straight saccharification
(SS) and simultaneous saccharification and fermentation (SSF) conditions following dilute sulfuric acid pretreatments designed
for optimum xylose yields. The optimum pretreatment conditions, within the constraints of the experimental system (Parr batch
reactor), were 1.2% acid, 180°C, and 0.5 min for switchgrass and 1% acid, 180°C, and 0.56 min for poplar. The cellulase enzyme
preparation was from Trichoderma reesei and fermentations were done with Saccharomyces cerevisiae. Time courses for SS were monitored as the sum of glucose and cellobiose; those for SSF as the sum of glucose, cellobiose,
and ethanol. Percentage conversions under SS conditions were 79.1% and 91.4% for the pretreated poplar and switchgrass feedstocks,
respectively. Analogous values under SSF conditions were 73.0% and 90.3% for pretreated poplar and switchgrass, respectively. 相似文献
2.
Christopher J. Barr B. Leif Hanson Kevin Click Grace Perrotta Constance A. Schall 《Cellulose (London, England)》2014,21(2):973-982
Varying ionic liquid, 1-ethyl 3-methyl imidazolium acetate, pretreatment incubation temperature on lignocellulosic biomass substrates, corn stover, switchgrass and poplar, can have dramatic effects on the enzymatic digestibility of the resultant regenerated biomass. In order to delineate the chemical and physical changes resulting from the pretreatment process and correlate changes with enzymatic digestibility, X-ray powder and fiber diffraction, 13C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy, and compositional analysis was completed on poplar, corn stover and switchgrass samples. Optimal pretreatment incubation temperatures were most closely associated with the retention of amorphous substrates upon drying of regenerated biomass. Maximal glucan to glucose conversion for 24 h enzyme hydrolysis was observed for corn stover, switchgrass and poplar at ionic liquid incubation temperatures of 100, 110 and 120 °C, respectively. We hypothesize that effective pretreatment temperatures must attain lignin redistribution and retention of xylan for optimal enzyme digestibility. 相似文献
3.
Hui Wang Radhakrishnan Srinivasan Fei Yu Philip Steele Qi Li Brian Mitchell Aditya Samala 《Applied biochemistry and biotechnology》2012,167(2):285-297
Bio-oil produced from biomass by fast pyrolysis has the potential to be a valuable substitute for fossil fuels. In a recent work on pinewood, we found that pretreatment alters the structure and chemical composition of biomass, which influence fast pyrolysis. In this study, we evaluated dilute acid, steam explosion, and size reduction pretreatments on sweetgum, switchgrass, and corn stover feedstocks. Bio-oils were produced from untreated and pretreated feedstocks in an auger reactor at 450?°C. The bio-oil??s physical properties of pH, water content, acid value, density, and viscosity were measured. The chemical characteristics of the bio-oils were determined by gas chromatography?Cmass spectrometry. The results showed that bio-oil yield and composition were influenced by the pretreatment method and feedstock type. Bio-oil yields of 52, 33, and 35?wt% were obtained from medium-sized (0.68?C1.532?mm) untreated sweetgum, switchgrass, and corn stover, respectively, which were higher than the yields from other sizes. Bio-oil yields of 56, 46, and 51?wt% were obtained from 1?% H2SO4-treated medium-sized sweetgum, switchgrass, and corn stover, respectively, which were higher than the yields from untreated and steam explosion treatments. 相似文献
4.
Vijay Sundaram Kasiviswanathan Muthukumarappan Stephen Gent 《Applied biochemistry and biotechnology》2017,181(3):1060-1079
Lignocellulosic feedstocks corn stover, prairie cord grass, and switchgrass were subjected to ammonia fiber expansion (AFEX?) pretreatment and densified using extrusion pelleting and ComPAKco densification technique. The effects of AFEX? pretreatment and densification were studied on the fast pyrolysis product yields. Feedstocks were milled in a hammer mill using three different screen sizes (2, 4, and 8 mm) and were subjected to AFEX? pretreatment. The untreated and AFEX?-pretreated feedstocks were moisture adjusted at three levels (5, 10, and 15 % wb) and were extruded using a lab-scale single screw extruder. The barrel temperature of the extruder was maintained at 75, 100, and 125 °C. Durability of the extruded pellets made from AFEX?-pretreated corn stover, prairie cord grass, and switchgrass varied from 94.5 to 99.2, 94.3 to 98.7, and 90.1 to 97.5 %, respectively. Results of the thermogravimetric analysis showed the decrease in the decomposition temperature of the all the feedstocks after AFEX? pretreatment indicating the increase in thermal stability. Loose and densified feedstocks were subjected to fast pyrolysis in a lab-scale reactor, and the yields (bio-oil and bio-char) were measured. Bio-char obtained from the AFEX?-pretreated feedstocks exhibited increased bulk and particle density compared to the untreated feedstocks. The properties of the bio-oil were statistically similar for the untreated, AFEX?-pretreated, and AFEX?-pretreated densified feedstocks. Based on the bio-char and bio-oil yields, the AFEX?-pretreated feedstocks and the densified AFEX?-pretreated feedstocks (pellets and PAKs) exhibited similar behavior. Hence, it can be concluded that densifying the AFEX?-pretreated feedstocks could be a viable option in the biomass-processing depots to reduce the transportation costs and the logistical impediments without affecting the product yields. 相似文献
5.
Effects of temperature and moisture on dilute-acid steam explosion pretreatment of corn stover and cellulase enzyme digestibility 总被引:3,自引:0,他引:3
Melvin P. Tucker Kyoung H. Kim Mildred M. Newman Quang A. Nguyen 《Applied biochemistry and biotechnology》2003,105(1-3):165-177
Corn stover is emerging as a viable feedstock for producing bioethanol from renewable resources. Dilute-acid pretreatment
of corn stover can solubilize a significant portion of the hemicellulosic component and enhance the enzymatic digestibility
of the remaining cellulose for fermentation into ethanol. In this study, dilute H2SO4 pretreatment of corn stover was performed in a steam explosion reactor at 160°C, 180°C, and 190°C, approx 1 wt% H2SO4, and 70-s to 840-s residence times. The combined severity (Log10 [R
o
] - pH), an expression relating pH, temperature, and residence time of pretreatment, ranged from 1.8 to 2.4. Soluble xylose
yields varied from 63 to 77% of theoretical from pretreatments of corn stover at 160 and 180°C. However, yields >90% of theoretical
were found with dilute-acid pretreatments at 190°C. A narrower range of higher combined severities was required for pretreatment
to obtain high soluble xylose yields when the moisture content of the acid-impregnated feedstock was increased from 55 to
63 wt%. Simultaneous saccharification and fermentation (SSF) of washed solids from corn stover pretreated at 190°C, using
an enzyme loading of 15 filter paper units (FPU)/g of cellulose, gave ethanol yields in excess of 85%. Similar SSF ethanol
yields were found using washed solid residues from 160 and 180°C pretreatments at similar combined severities but required
a higher enzyme loading of approx 25 FPU/g of cellulose. 相似文献
6.
Binod Rijal Gwen Biersbach William R. Gibbons Scott W. Pryor 《Applied biochemistry and biotechnology》2014,174(2):845-854
Switchgrass (SG), corn stover (CS), and prairie cordgrass (PCG) pretreated with ammonia fiber expansion (AFEX) were densified using a novel low-temperature, low-pressure densification method. Simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF) were performed with loose and densified AFEX-treated biomass to determine the effect of post-AFEX densification. Biomass particle size reduction before pretreatment increased 144-h SSF ethanol yields from densified material by 8–9 % although no significant differences were seen in the first 72 h. Grinding material after densification had no impact on final ethanol yields but increased production rates in the first 24–48 h. Low-pressure, post-AFEX densification had no adverse effects on SSF ethanol yields from SG or CS but reduced yields from densified PCG by 16 %. Glucose concentrations after hydrolysis (SHF) showed similar trends. Ethanol yields after SHF, however, showed that densification had no significant impact on CS or PCG but reduced final ethanol yields from SG. 相似文献
7.
Corn stover silage is an attractive raw material for the production of biofuels and chemicals due to its high content of carbohydrates
and easy degradability. The effects of Fe(NO3)3 pretreatment conditions on sugar yields were investigated for corn stover silage. In addition, a combined severity factor
was used to evaluate the effect of pretreatment conditions on the concentration of total sugars and inhibitors. Optimum pretreatment
condition was obtained at 150 °C for 10 min with 0.05 M Fe(NO3)3, at which the yields of soluble xylose and glucose in liquid achieved 91.80% of initial xylose, 96.74% of initial arabinose
and 19.09% of initial glucose, respectively, meanwhile, 91.84% of initial xylose, 98.24% of initial arabinose, and 19.91%
of initial glucose were removed. In addition, a severity analysis showed that the maximum sugar concentration of 33.48 g/l
was achieved at combined severity parameter value of 0.62, while the inhibitor concentration was only 0.03 g/l. Fe(NO3)3 is an effective catalyst to enhance hemicellulose hydrolysis in corn stover silage, the yields of monomeric xylose in the
liquid fraction reached as high as 91.06% of initial xylose and 96.22% of initial arabinose, respectively. 相似文献
8.
Pretreatment based on aqueous ammonia was investigated under two different modes of operation: soaking in aqueous ammonia
and ammonia recycle percolation. These processes were applied to three different feedstocks with varied composition: corn
stover, high lignin (HL), and low lignin (LL) hybrid poplars. One of the important features of ammonia-based pretreatment
is that most of the hemicellulose is retained after treatment, which simplifies the overall bioconversion process and enhances
the conversion efficiency. The pretreatment processes were optimized for these feedstocks, taking carbohydrate retention as
well as sugar yield in consideration. The data indicate that hybrid poplar is more difficult to treat than corn stover, thus,
requires more severe conditions. On the other hand, hybrid poplar has a beneficial property that it retains most of the hemicellulose
after pretreatment. To enhance the digestibility of ammonia-treated poplars, xylanase was supplemented during enzymatic hydrolysis.
Because of high retention of hemicellulose in treated hybrid poplar, xylanase supplementation significantly improved xylan
as well as glucan digestibility. Of the three feedstocks, best results and highest improvement by xylanase addition was observed
with LL hybrid poplar, showing 90% of overall sugar yield. 相似文献
9.
Daniel J. Schell Jody Farmer Millie Newman James D. McMillan 《Applied biochemistry and biotechnology》2003,105(1-3):69-85
Corn stover is a domestic feedstock that has potential to produce significant quantities of fuel ethanol and other bioenergy
and biobased products. However, comprehensive yield and carbon mass balance information and validated kinetic models for dilute-sulfuric
acid (H2SO4) pretreatment of corn stover have not been available. This has hindered the estimation of process economics and also limited
the ability to perform technoeconomic modeling to guide research. To better characterize pretreatment and assess its kinetics,
we pretreated corn stover in a continuous 1 t/d reactor. Corn stover was pretreated at 20% (w/w) solids concentration over
a range of conditions encompassing residence times of 3–12 min, temperatures of 165–195°C, and H2SO4 concentrations of 0.5–1.4% (w/w). Xylan conversion yield and carbon mass balance data were collected at each run condition.
Performance results were used to estimate kinetic model parameters assuming biphasic hemicellulose hydrolysis and a hydrolysis
mechanism incorporating formation of intermediate xylo-oligomers. In addition, some of the pretreated solids were tested in
a simultaneous saccharification and fermentation (SSF) process to measure the reactivity of their cellulose component to enzymatic
digestion by cellulase enzymes. Monomeric xylose yields of 69–71% and total xylose yields (monomers and oligomers) of 70–77%
were achieved with performance level depending on pretreatment severity. Cellulose conversion yields in SSF of 80–87% were
obtained for some of the most digestible pretreated solids. 相似文献
10.
Pretreatment of corn stover by soaking in aqueous ammonia 总被引:1,自引:0,他引:1
Soaking in aqueous ammonia (SAA) was investigated as a pretreatment method for corn stover. In this method, the feedstock
was soaked in aqueous ammonia over an extended period (10–60 d) at room temperature. It was done without agitation at atmospheric
pressure. SAA treatment removed 55–74% of the lignin, but retained nearly 100% of the glucan and 85% of the xylan. The xylan
remaining in the corn stover after SAA treatment was hydrolyzed along with the glucan by xylanase present in the Spezyme CP
enzyme. In the simultaneous saccharification and fermentation (SSF) test of SAA-treated corn stover, using S. cerevisiae (D5A), an ethanol yield of 73% of theoretical maximum was obtained on the basis of the glucan content in the treated corn stover.
The accumulation of xylose in the SSF appears to inhibit the cellulase activity on glucan hydrolysis, which limits the yield
of ethanol. In the simultaneous saccharification and co-fermentation (SSCF) test, using recombinant E. coli (KO11), both the glucan and xylose were effectively utilized, resulting in on overall ethanol yield of 77% based on the glucan
and xylan content of the substrate. When the SSCF process is used, the fact that the xylan fraction is retained during pretreatment
is a desirable feature since the overall bioconversion can be carried out in a single step without separate recovery of xylose
from the pretreatment liquid. 相似文献
11.
Ball Milling Pretreatment of Corn Stover for Enhancing the Efficiency of Enzymatic Hydrolysis 总被引:2,自引:0,他引:2
Zengxiang Lin He Huang Hongman Zhang Lin Zhang Lishi Yan Jingwen Chen 《Applied biochemistry and biotechnology》2010,162(7):1872-1880
Ethanol can be produced from lignocellulosic biomass with the usage of ball milling pretreatment followed by enzymatic hydrolysis
and fermentation. The sugar yields from lignocellulosic feed stocks are critical parameters for ethanol production process.
The research results from this paper indicated that the yields of glucose and xylose were improved by adding any of the following
dilute chemical reagents: H2SO4, HCl, HNO3, CH3COOH, HCOOH, H3PO4, and NaOH, KOH, Ca(OH)2, NH3·H2O in the ball milling pretreatment of corn stover. The optimal enzymatic hydrolysis efficiencies were obtained under the conditions
of ball milling in the alkali medium that was due to delignification. The data also demonstrated that ball milling pretreatment
was a robust process. From the microscope image of ball milling-pretreated corn stover, it could be observed that the particle
size of material was decreased and the fiber structure was more loosely organized. Meanwhile, the results indicate that the
treatment effect of wet milling is better than that of dry milling. The optimum parameters for the milling process were ball
speed of 350 r/min, solid/liquid ratio of 1:10, raw material particle size with 0.5 mm, and number of balls of 20 (steel ball,
Φ = 10 mm), grinding for 30 min. In comparison with water milling process, alkaline milling treatment could increase the enzymatic
hydrolysis efficiency of corn stover by 110%; and through the digestion process with the combination of xylanase and cellulase
mixture, the hydrolysis efficiency could increase by 160%. 相似文献
12.
Improving the quality of cellulosic ethanol feedstocks through breeding and genetic manipulation could significantly impact
the economics of this industry. Attaining this will require comprehensive and rapid characterization of large numbers of samples.
There are many similarities between improving corn silage quality for dairy production and improving feedstock quality for
cellulosic ethanol. It was our objective to provide insight into what is needed for genetic improvement of cellulosic feedstocks
by reviewing the development and operation of a corn silage breeding program. We discuss the evolving definition of silage
quality and relate what we have learned about silage quality to what is needed for measuring and improving feedstock quality.
In addition, repeatability estimates of corn stover traits are reported for a set of hybrids. Repeatability of theoretical
ethanol potential measured by near-infrared spectroscopy is high, suggesting that this trait may be easily improved through
breeding. Just as cell wall digestibility has been factored into the latest measurements of silage quality, conversion efficiency
should be standardized and included in indices of feedstock quality to maximize overall, economical energy availability. 相似文献
13.
Treatment of corn stover with aqueous ammonia removes most of the structural lignin, whereas retaining the majority of the carbohydrates in the solids. After treatment, both the cellulose and hemicellulose in corn stover become highly susceptible to enzymatic digestion. In this study, corn stover treated by aqueous ammonia was investigated as the substrate for lactic acid production by simultaneous saccharification and cofermentation (SSCF). A commercial cellulase (Spezyme-CP) and Lactobacillus pentosus American Type Culture Collection (ATCC) 8041 (Spanish Type Culture Collection [CECT]-4023) were used for hydrolysis and fermentation, respectively. In batch SSCF operation, the carbohydrates in the treated corn stover were converted to lactic acid with high yields, the maximum lactic acid yield reaching 92% of the stoichiometric maximum based on total fermentable carbohydrates (glucose, xylose, and arabinose). A small amount of acetic acid was also produced from pentoses through the phosphoketolase pathway. Among the major process variables for batch SSCF, enzyme loading and the amount of yeast extract were found to be the key factors affecting lactic acid production. Further tests on nutrients indicated that corn steep liquor could be substituted for yeast extract as a nitrogen source to achieve the same lactic acid yield. Fed-batch operation of the SSCF was beneficial in raising the concentration of lactic acid to a maximum value of 75.0 g/L. 相似文献
14.
Bagasse, corn husk, and switchgrass were pretreated with ammonia water to enhance enzymatic hydrolysis. The sample (2 g) was
mixed with 1–6 mL ammonia water (25–28% ammonia) and autoclaved at 120°C for 20 min. After treatment, the product was vacuum-dried
to remove ammonia gas. The dried solid could be used immediately in the enzymatic hydrolysis without washing. The enzymatic
hydrolysis was effectively improved with more than 0.5 and 1 mL ammonia water/g for corn husk and bagasse, respectively. In
bagasse, glucose, xylose, and xylobiose were the main products. The adsorption of CMCase and xylanase was related to the initial
rate of enzymatic hydrolysis. In corn husks, arabinoxylan extracted by pretreatment was substantially unhydrolyzed because
of the high ratio of arabinose to xylose (0.6). The carbohydrate yields from cellulose and hemicellulose were 72.9% and 82.4%
in bagasse, and 86.2% and 91.9% in corn husk, respectively. The ammonia/water pretreatment also benefited from switchgrass
(Miscanthus sinensis and Solidago altissima L.) hydrolysis. 相似文献
15.
Zhuang Zuo Shen Tian Zebing Chen Jia Li Xiushan Yang 《Applied biochemistry and biotechnology》2012,167(7):2088-2102
The production of ethanol and methane from corn stover (CS) was investigated in a biorefinery process. Initially, a novel soaking pretreatment (NaOH and aqueous-ammonia) for CS was developed to remove lignin, swell the biomass, and improve enzymatic digestibility. Based on the sugar yield during enzymatic hydrolysis, the optimal pretreatment conditions were 1?% NaOH?+?8?% NH4OH, 50°C, 48?h, with a solid-to-liquid ratio 1:10. The results demonstrated that soaking pretreatment removed 63.6?% lignin while reserving most of the carbohydrates. After enzymatic hydrolysis, the yields of glucose and xylose were 78.5?% and 69.3?%, respectively. The simultaneous saccharification and fermentation of pretreated CS using Pichia stipitis resulted in an ethanol concentration of 36.1?g/L, corresponding only to 63.3?% of the theoretical maximum. In order to simplify the process and reduce the capital cost, the liquid fraction of the pretreatment was used to re-soak new CS. For methane production, the re-soaked CS and the residues of SSF were anaerobically digested for 120?days. Fifteen grams CS were converted to 1.9?g of ethanol and 1337.3?mL of methane in the entire process. 相似文献
16.
Mahesh S. Krishnan Nancy W. Y. Ho George T. Tsao 《Applied biochemistry and biotechnology》1999,78(1-3):373-388
Fermentation kinetics of ethanol production from glucose, xylose, and their mixtures using a recombinant Saccharomyces 1400 (pLNH33) are reported. Single-substrate kinetics indicate that the specific growth rate of the yeast and the specific
ethanol productivity on glucose as the substrate was greater than on xylose as a substrate. Ethanol yields from glucose and
xylose fermentation were typically 95 and 80% of the theoretical yield, respectively. The effect of ethanol inhibition is
more pronounced for xylose fermentation than for glucose fermentation. Studies on glucose-xylose mixtures indicate that the
recombinant yeast co-ferments glucose and xylose. Fermentation of a 52.8 g/L glucose and 56.3 g/L xylose mixture gave an ethanol
concentration of 47.9 g/L after 36 h. Based on a theoretical yield of 0.51 g ethanol/g sugars, the ethanol yield from this
experiment (for data up to 24 h) was calculated to be 0.46 g ethanol/g sugar or 90% of the theoretical yield. The specific
growth rate of the yeast on glucose-xylose mixtures was found to lie between the specific growth rate on glucose and the specific
growth rate on xylose. Kinetic studies were used to develop a fermentation model incorporating the effects of substrate inhibition,
product inhibition, and inoculum size. Good agreements were obtained between model predictions and experimental data from
batch fermentation of glucose, xylose, and their mixtures. 相似文献
17.
The relationships between biomass composition, water retention value (WRV), settling volume and enzymatic glucose yield and enzyme binding is investigated in this work by employing grasses pretreated with combinations of alkaline hydrogen peroxide (AHP) delignification and liquid hot water pretreatment that result in significant alterations of cell wall properties and subsequent enzymatic hydrolysis yields. Specifically, these cell wall treatments are performed on corn stover and switchgrass to generate material with a range of lignin (6–35 %) and xylan (2–28 %) contents as well as a range of other properties such as carboxylic acid content, water binding affinity and swellability. It was determined that WRV and settling volume are predictors of glucose yield (R2 = 0.900 and 0.895 respectively) over the range of materials and treatment conditions used. It was also observed that mild AHP delignification can result in threefold increases in the WRV. Dynamic vapor sorption isotherms demonstrated that AHP-delignified corn stover exhibited an increased affinity for water sorption from the vapor phase relative to untreated corn stover. These results indicate that these water properties may be useful proxies for biomass susceptibility to enzymatic deconstruction. 相似文献
18.
Liang Zhang Xiaoqing Wang Zhenhua Ruan Ying Liu Xiaorui Niu Zhengbo Yue Zhimin Li Wei Liao Yan Liu 《Applied biochemistry and biotechnology》2014,172(2):1045-1054
Three pretreated corn stover (ammonia fiber expansion, dilute acid, and dilute alkali) were used as carbon source to culture Trichoderma reesei Rut C-30 for cellulase and xylanase production. The results indicated that the cultures on ammonia fiber expansion and alkali pretreated corn stover had better enzyme production than the acid pretreated ones. The consequent enzymatic hydrolysis was performed applying fungal enzymes on pretreated corn stover samples. Tukey’s statistical comparisons exhibited that there were significant differences on enzymatic hydrolysis among different combination of fungal enzymes and pretreated corn stover. The higher sugar yields were achieved by the enzymatic hydrolysis of dilute alkali pretreated corn stover. 相似文献
19.
The advantages of the use of SO2 in steam pretreatment are described. Two different large scale continuous reactors, the Stake and the Wenger, have been used
for this purpose. Pine, aspen and corn stover were prehydrolysed by SO2 in these reactors and hydrolysed by enzymes. The solution of hexoses and pentoses so obtained were fermented byPichia stipitis R, yielding 372, 346 and 388 L ethanol/tonne for the 3 feedstocks, respectively. When a mixed culture ofP. stipitis R, which is an excellent pentose fermenter, andBrettanomyces clausenii which is an excellent cellobiose fermenter, was used in a simultaneous saccharification-fermentation made with SO2-prehydrolysed aspen, the yield rose to 384 L/tonne. These are higher yields than have been reported in the literature to
date. 相似文献
20.
Microbial lipid is a promising source of oil to produce biofuel if it can be generated from lignocellulosic materials. Mortierella isabellina is a filamentous fungal species featuring high content of oil in its cell biomass. In this work, M. isabellina was studied for lipid production from corn stover. The experimental results showed that M. isabellina could grow on different kinds of carbon sources including xylose and acetate, and the lipid content reached to 35 % at C/N ratio of 20. With dilution, M. isabellina could endure inhibition effects by dilute acid pretreatment of corn stover (0.3 g/L furfural, 1.2 g/L HMF, and 1 g/L 4-hydroxybenozic acid) and the strain formed pellets in the cell cultivations. An integrated process was developed combining the dilute acid pretreatment, cellulase hydrolysis, and cell cultivation for M. isabellina to convert corn stover to oil containing fungal biomass. With 7.5 % pretreated biomass solid loading ratio, the final lipid yield from sugar in pretreated biomass was 40 % and the final lipid concentration of the culture reached to 6.46 g/L. 相似文献