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1.
The aim of this work was to optimize the enzymatic hydrolysis of the cellulose fraction of cashew apple bagasse (CAB) after diluted acid (CAB-H) and alkali pretreatment (CAB-OH), and to evaluate its fermentation to ethanol using Saccharomyces cerevisiae. Glucose conversion of 82?±?2 mg/g CAB-H and 730?±?20 mg/g CAB-OH was obtained when 2% (w/v) of solid and 30 FPU/g bagasse was used during hydrolysis at 45 °C, 2-fold higher than when using 15 FPU/g bagasse, 44?±?2 mg/g CAB-H, and 450?±?50 mg/g CAB-OH, respectively. Ethanol concentration and productivity, achieved after 6 h of fermentation, were 20.0?±?0.2 g L?1 and 3.33 g L?1 h?1, respectively, when using CAB-OH hydrolyzate (initial glucose concentration of 52.4 g L?1). For CAB-H hydrolyzate (initial glucose concentration of 17.4 g L?1), ethanol concentration and productivity were 8.2?±?0.1 g L?1 and 2.7 g L?1 h?1 in 3 h, respectively. Hydrolyzates fermentation resulted in an ethanol yield of 0.38 and 0.47 g/g glucose with pretreated CAB-OH and CAB-H, respectively. Ethanol concentration and productivity, obtained using CAB-OH hydrolyzate, were close to the values obtained in the conventional ethanol fermentation of cashew apple juice or sugar cane juice.  相似文献   

2.
In this work, cashew apple bagasse (CAB) was used for Saccharomyces cerevisiae immobilization. The support was prepared through a treatment with a solution of 3% HCl, and delignification with 2% NaOH was also conducted. Optical micrographs showed that high populations of yeast cells adhered to pre-treated CAB surface. Ten consecutive fermentations of cashew apple juice for ethanol production were carried out using immobilized yeasts. High ethanol productivity was observed from the third fermentation assay until the tenth fermentation. Ethanol concentrations (about 19.82–37.83 g L?1 in average value) and ethanol productivities (about 3.30–6.31 g L?1 h?1) were high and stable, and residual sugar concentrations were low in almost all fermentations (around 3.00 g L?1) with conversions ranging from 44.80% to 96.50%, showing efficiency (85.30–98.52%) and operational stability of the biocatalyst for ethanol fermentation. Results showed that cashew apple bagasse is an efficient support for cell immobilization aiming at ethanol production.  相似文献   

3.
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 gglucan−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 gCAB-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   

4.
Actinobacillus succinogenes 130 Z was used to produce succinic acid from cheese whey in this study. At the presence of external CO2 supply, the effects of initial cheese whey concentration, pH, and inoculum size on the succinic acid production were studied. The by-product formation during the fermentation process was also analyzed. The highest succinic acid yield of 0.57 was obtained at initial cheese whey concentration of 50 g/L, while the highest succinic acid productivity of 0.58 g h−1 L−1 was obtained at initial cheese whey concentration of 100 g/L. Increase in pH and inoculum size caused higher succinic acid yield and productivity. At the preferred fermentation condition of pH 6.8, inoculum size of 5% and initial cheese whey concentration of 50 g/L, succinic acid yield of 0.57, and productivity of 0.44 g h−1 L−1 were obtained. Acetic acid and formic acid were the main by-products throughout the fermentation run of 48 h. It is feasible to produce succinic acid using lactose from cheese whey as carbon resource by A. succinogenes 130 Z.  相似文献   

5.
Butyric acid has many applications in chemical, food, and pharmaceutical industries. In the present study, Clostridium tyrobutyricum ATCC 25755 was immobilized in a fibrous-bed bioreactor to evaluate the performance of butyrate production from glucose and xylose. The results showed that the final concentration and yield of butyric acid were 13.70 and 0.46 g g−1, respectively, in batch fermentation when 30 g L−1 glucose was introduced into the bioreactor. Furthermore, high concentration 10.10 g L−1 and yield 0.40 g g−1 of butyric acid were obtained with 25 g L−1 xylose as the carbon source. The immobilized cells of C. tyrobutyricum ensured similar productivity and yield from repeated batch fermentation. In the fed-batch fermentation, the final concentration of butyric acid was further improved to 24.88 g L−1 with one suitable glucose feeding in the fibrous-bed bioreactor. C. tyrobutyricum immobilized in the fibrous-bed bioreactor would provide an economically viable fermentation process to convert the reducing sugars derived from plant biomass into the final bulk chemical (butyric acid).  相似文献   

6.
A fed-batch culture system with constant feeding (glucose 80 g L−1, 0.25 ml min−1) was used to study the influence of glucose on cell dry weight and exopolysaccharides production from submerged Tremella fuciformis spores in a 5-L stirred-tank bioreactor. The results showed that high levels of cell mass (9.80 g L−1) and exopolysaccharides production (3.12 g L−1) in fed-batch fermentation were obtained after 1 h of feeding, where the specific growth rate (μ) and exopolysaccharides yield on substrate consumed (YP/S) were 0.267 d−1 and 0.14 g g−1. Unlike batch fermentation, maximal cell mass and exopolysaccharides production merely reached 7.11 and 2.08 g L−1; the specific growth rate (μ) and exopolysaccharides yield on substrate consumed (YP/S) were 0.194 d−1 and 0.093 g g−1, respectively. It is concluded that the synthesis of exopolysaccharides can be promoted effectively when feeding glucose at a late exponential phase.  相似文献   

7.
In this study, we evaluated the feasibility of solid-state fermentation (SSF) on polyurethane foam (PUF) for xanthan production. The effects of air pressure pulsation (APP) on biomass accumulation and final xanthan concentration were also studied. Under suitable conditions (15% inoculum, 0.5-cm (side length) PUF cubes, 15 mL medium per gram cubes and 4.5 cm bed depth), the broth was dispersed on the PUF as a film. When the initial glucose concentration in the media was low (20 and 40 g L−1), there was no significant difference between the final xanthan concentration in static SSF and submerged fermentation (SMF). When high initial glucose concentrations (60 and 80 g L−1) were used, the final gum concentrations in SSF were much higher than those in SMF. When the APP technique was applied in xanthan production with a medium containing a high glucose concentration (80 g L−1), the oxygen consumption rate of Xanthomonas campestris was significantly enhanced at the later stages of fermentation, and both the biomass and xanthan concentration were improved. The results indicated that SSF on PUF is suitable for xanthan preparation, especially when the initial glucose concentration ranged from 60 to 80 g L−1. Those results also demonstrated that APP technology can be used to enhance xanthan yields.  相似文献   

8.
Substrate concentration in lactic acid fermentation broth could not be controlled well by traditional feeding methods, including constant, intermittent, and exponential feeding methods, in fed-batch experiments. A simple feedback feeding method based on pH was proposed to control pH and substrate concentration synchronously to enhance lactic acid production in fed-batch culture. As the linear relationship between the consumption amounts of alkali and that of substrate was concluded during lactic acid fermentation, the alkali and substrate in the feeding broth were mixed together proportionally. Thus, the concentration of substrate could be controlled through the adjustment of pH automatically. In the fed-batch lactic acid fermentation with Lactobacillus lactis-11 by this method, the residual glucose concentration in fermentation broth was controlled between 4.1 and 4.9 g L−1, and the highest concentration of lactic acid, maximum cell dry weight, volumetric productivity of lactic acid, and yield were 96.3 g L−1, 4.7 g L−1, 1.9 g L−1 h−1, and 0.99 g lactic acid per gram of glucose, respectively, compared to 82.7 g L−1, 3.31 g L−1, 1.7 g L−1 h−1, and 0.92 g lactic acid per gram of glucose in batch culture. This feeding method was simple and easily operated and could be feasible for industrial lactic acid production in the future.  相似文献   

9.
Recent work has identified ethanol toxicity as a major factor preventing continuous production of ethanol at the concentrations obtainable in batch culture. In this paper we investigate the use of a continuous two-stage bioreactor design to circumvent toxic effects of ethanol. Biomass is produced via continuous culture in the first stage reactor in which ethanol concentrations are either absent or maintained at low levels. The freshly grown cells are fed into the second bioreactor in which high ethanol concentrations are produced. The steady influx of fresh cells and continuous removal of spent cells helps minimize the loss of fermentative activity that results from anaerobiosis and exposure to high ethanol concentrations. A final ethanol concentration of 37 g L−1 and overall yield of .32 g g−1 were obtained with the two-stage reactor as compared to corresponding values of 38 g L−1 and .32 g g−1 obtained in batch. The volumetric rate in the two-state process was .96 g L−1 as compared to .46 g L−1 h−1 in batch. Maintained in cooperation with the University of Wisconsin-Madison. The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the US Department of Agriculture of any product or service to the exclusion of others which may be suitable.  相似文献   

10.
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   

11.
The ability of Xanthomonas campestris to convert glucose and xylose to xanthan and the structure of xanthan derived from the glucose/xylose mixture media are important when the lignocelluloses hydrolysate was used in xanthan production. In this paper, the features related to xanthan fermentation in the glucose/xylose mixture media and the structures of xanthan derived from the mixture media were studied. Glucose was the preferred carbon source to produce xanthan while xylose was also utilized with a very low consumption rate. When the fraction of glucose decreased from 100% to 25%, the glucose consumption rate and xanthan production rate reduced from 0.44 g L−1 h−1 to 0.25 g L−1 h−1 and 0.21 g L−1 h−1 to 0.04 g L−1 h−1 respectively while xylose was consumed at a very stable rate (0.053–0.060 g L−1 h−1). On the other hand, when the xylose fraction increased from 0% to 50%, pyruvate and acetate content of xanthan increased from 2.43% to 3.78% and 2.55% to 7.05%. The existence of xylose also led to higher average molecular weight. Therefore, it could be concluded that xylose was not efficiently utilized by X. campestris to produce xanthan. The concentration of glucose rather than the total sugar was the main factor to determine the xanthan production. But xylose was helpful to improve the quality of xanthan.  相似文献   

12.
The fermentation characteristics of a recombinant strain of Zymomonas mobilis ZM4(pZB5) capable of converting both glucose and xylose to ethanol have been further investigated. Previous studies have shown that the strain ZM4(pZB5) was capable of converting a mixture o 65 g/L of glucose and 65 g/L of xylose to 62 g/L of ethanol in 48 h with an overall yield of 0.46 g/g. Higher sugar concentrations (e.g., 75/75 g/L) resulted in incomplete xylose utilization (80 h). In the present study, further kinetic evaluations at high sugar levels are reported. Acetate inhibition studies and evaluation of temperature and pH effects indicated increased maximum specific uptake rates of glucose and xylose under stressed conditions with increased metabolic uncoupling. A high-productivity system was developed that involved a membrane bioreactor with cell recycling. At sugar concentrations of approx 50/50 g/L of glucose/xylose, an ethanol concentration of 50 g/L, an ethanol productivity of approx 5 g/(L·h), and a yield (Y p/s) of 0.50 g/g were achieved. Decreases in cell viability were found in this system after attainment of an initial steady state (40–60 h); a slow bleed of concentrated cells may be required to overcome this problem.  相似文献   

13.
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   

14.
Bacillus subtilis LAMI008 strain isolated from the tank of Chlorination at the Wastewater Treatment Plant on Campus do Pici in Federal University of Ceará, Brazil has been screened for surfactin production in mineral medium containing clarified cashew apple juice (MM-CAJC). Results were compared with the ones obtained using mineral medium with glucose PA as carbon source. The influence on growth and surfactin production of culture medium supplementation with yeast extract was also studied. The substrate concentration analysis indicated that B. subtilis LAMI008 was able to degrade all carbon sources studied and produce biosurfactant. The highest reduction in surface tension was achieved with the fermentation of MM-CAJC, supplemented with yeast extract, which decreased from 58.95?±?0.10 to 38.10?±?0.81 dyn cm?1. The biosurfactant produced was capable of emulsifying kerosene, achieving an emulsification index of 65%. Surfactin concentration of 3.5 mg L?1 was obtained when MM-CAJC, supplemented with yeast extract, was used, thus indicating that it is feasible to produce surfactin from clarified cashew apple juice, a renewable and low-cost carbon source.  相似文献   

15.
We explored the influence of dilution rate and pH in continuous cultures of Clostridium acetobutylicum. A 200-mL fibrous bed bioreactor was used to produce high cell density and butyrate concentrations at pH 5.4 and 35°C. By feeding glucose and butyrate as a cosubstrate, the fermentation was maintained in the solventogenesis phase, and the optimal butanol productivity of 4.6g/(L h) and a yield of 0.42 g/g were obtained at a dilution rate of 0.9h−1 and pH 4.3. Compared to the conventional acetone-butanol-ethanol fermentation, the new fermentation process greatly improved butanol yield, making butanol production from corn an attractive alternative to ethanol fermentation.  相似文献   

16.
This work presents a continuous simultaneous saccharification and fermentation (SSF) process to produce ethanol from starch using glucoamylase and Saccharomyces cerevisiae co-immobilized in pectin gel. The enzyme was immobilized on macroporous silica, after silanization and activation of the support with glutaraldehyde. The silica–enzyme derivative was co-immobilized with yeast in pectin gel. This biocatalyst was used to produce ethanol from liquefied manioc root flour syrup, in three fixed bed reactors. The initial reactor yeast load was 0.05 g wet yeast/ml of reactor (0.1 g wet yeast/g gel), used in all SSF experiments. The enzyme concentration in the reactor was defined by running SSF batch assays, using different amount of silica–enzyme derivative, co-immobilized with yeast in pectin gel. The chosen reactor enzyme concentration, 3.77 U/ml, allowed fermentation to be the rate-limiting step in the batch experiment. In this condition, using initial substrate concentration of 166.0 g/l of total reducing sugars (TRS), 1 ml gel/1 ml of medium, ethanol productivity of 8.3 g/l/h was achieved, for total conversion of starch to ethanol and 91% of the theoretical yield. In the continuous runs, feeding 163.0 g/l of TRS and using the same enzyme and yeast concentrations used in the batch run, ethanol productivity was 5.9 g ethanol/l/h, with 97% of substrate conversion and 81% of the ethanol theoretical yield. Diffusion effects in the extra-biocatalyst film seemed to be reduced when operating at superficial velocities above 3.7 × 10−4 cm/s.  相似文献   

17.
The effect of the shear rate on pullulan production from beet molasses by Aureobasidium pullulans P56 in an airlift reactor was investigated. A maximum polysaccharide concentration (18.5 g/L), biomass dry weight (14.0 g/L), polysaccharide yield (38.5%), and sugar utilization (96%) was achieved at a shear rate of 42 s−1. A. pullulans grown on beet molasses produced a mixture of pullulan and other polysaccharides. The highest value of pullulan proportion (30% of total polysaccharide) was obtained at a low shear rate (42 s−1). The apparent viscosity of the fermentation broth increased as the shear rate increased up to 42 s−1 and then decreased. On the other hand, the dissolved oxygen concentration and the volumetric mass transfer coefficient increased with the increase of the shear rate from 21 to 84 s−1. The external addition of L-glutamic acid, olive oil, and Tween-80 improved significantly the production of crude polysaccharide (27.0 g/L), but the pullulan content of the polysaccharide was low (20%).  相似文献   

18.
The production of pullulan from beet molasses by a pigment-free strain of Aureobasidium pullulans on shake-flask culture was investigated. Combined pretreatment of molasses with sulfuric acid and activated carbon to remove potential fermentation inhibitors present in molasses resulted in a maximum pullulan concentration of 24 g/L, a biomass dry wt of 14 g/L, a pullulan yield of 52.5%, and a sugar utilization of 92% with optimum fermentation conditions (initial sugar concentration of 50 g/L and initial pH of 7.0). The addition of other nutrients as carbon and nitrogen supplements (olive oil, ammonium sulfate, yeast extract) did not further improve the production of the exopolysaccharides. Structural characterization of the isolated polysaccharides from the fermentation broths by 13C-nuclear magnetic resonance spectroscopy and pullulanase digestion combined with size-exclusion chromatography confirmed the identity of pullulan and the homogeneity (>93% dry basis) of the elaborated polysaccharides by the microorganism. Using multiangle laser light scattering and refractive index detectors in conjunction with high-performance size-exclusion chromatography molecular size distributions and estimates of the molecular weight (M w =2.1−4.1×105), root mean square of the radius of gyration (R g =30−38 nm), and polydispersity index (M w /M n =1.4−2.4) were obtained. The fermentation products of molasses pretreated with sulfuric acid and/or activated carbon were more homogeneous and free of contaminating proteins. In the concentration range of 2.8−10.0 (w/v), the solution’s rheologic behavior of the isolated pullulans was almost Newtonian (within 1 and 1200 s−1 at 20°C); a slight shear thinning was observed at 10.0 (w/v) for the high molecular weight samples. Overall, beet molasses pretreated with sulfuric acid and activated carbon appears as an attractive fermentation medium for the production of pullulan by A. pullulans.  相似文献   

19.
A mutant strain ofPichia stipitis, FPL-061, was obtained by selecting for growth on L-xylose in the presence of respiratory inhibitors. The specific fermentation rate of FPL-061, was higher than that of the parent,Pichia stipitis CBS 6054, because of its lower cell yield and growth rate and higher specific substrate uptake rate. With a mixture of glucose and xylose, the mutant strain FPL-061 produced 29.4 g ethanol/L with a yield of 0.42 g ethanol/g sugar consumed. By comparison, CBS 6054 produced 25.7 g ethanol/L with a yield of 0.35 gJg. The fermentation was most efficient at an aeration rate of 9.2 mmoles O2 L-1 h-1. At high aeration rates (22 mmoles O2 L-1 h-1), the mutant cell yield was less than that of the parent. At low aeration rates, (1.1 to 2.5 O2 L-1 h-1), cell yields were similar, the ethanol formation rates were low, and xylitol accumulation was observed in both the strains. Both strains respired the ethanol once sugar was exhausted. We infer from the results that the mutant, P.stipitis FPL-061, diverts a larger fraction of its metabolic energy from cell growth into ethanol production.  相似文献   

20.
With the objective of determining the kinetic behavior (growth, substrate, pH, and carotenoid production) and obtain the stoichiometric parameters of the fermentative process by Sporidiobolus salmonicolor in synthetic and agroindustrial media, fermentations were carried out in shaken flasks at 25°C, 180 rpm, and initial pH of 4.0 for 120 h in the dark, sampling every 6 h. The maximum concentrations of total carotenoids in synthetic (913 μg/L) and agroindustrial (502 μg/L) media were attained approximately 100 h after the start of the fermentative process. Carotenoid bioproduction is associated with cell growth and the ratio between carotenoid production and cell growth (Y P/X) is 176 and 163 μg/g in the synthetic and agroindustrial media, respectively. The pH of the agroindustrial fermentation medium varied from 4.2 to 8.5 during the fermentation. The specific growth rate (μ X) for S. salmonicolor in synthetic and agroindustrial media was 0.07 and 0.04 h−1, respectively. The synthetic medium allowed for greater productivity, obtaining maximum cell productivity (P x) of 0.08 g L−1 h−1 and maximum total carotenoid productivity (P car) of 14.2 μg L−1 h−1. Knowledge of the kinetics of a fermentative process is of extreme importance when transposing a laboratory experiment to an industrial scale, as well as making a quantitative comparison between different culture conditions.  相似文献   

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