Effect of Agitation Rate on Ethanol Production from Sugar Maple Hemicellulosic Hydrolysate by Pichia stipitis

Concentrated dilute acid hydrolysate was obtained from hot water extracts of Acer saccharum (sugar maple) and was fermented to ethanol by Pichia stipitis in a 1.3-L-benchtop bioreactor. The conditions under which the highest ethanol yield was achieved were when the air flow rate was set to 100?cm³ and the agitation rate was set to 150?rpm resulting in an overall mass transfer coefficient (K _L a) of 0.108?min^?1. A maximum ethanol concentration of 29.7?g/L was achieved after 120?h of fermentation; however, after 90?h of fermentation, the ethanol concentration was only slightly lower at 29.1?g/L with a yield of 0.39?g ethanol per gram of sugar consumed. Using the same air flow rate and adjusting the agitation rate resulted in lower ethanol yields of 0.25?g/g at 50?rpm and 0.30?g/g at 300?rpm. The time it takes to reach the maximum ethanol concentration was also affected by the agitation rate. The ethanol concentration continued to increase even after 130?h of fermentation when the agitation rate was set at 50?rpm, whereas the maximum ethanol concentration was reached after only 68.5?h at 300?rpm.     

Ethanol Production from Sugarcane Bagasse by Zymomonas mobilis Using Simultaneous Saccharification and Fermentation (SSF) Process

Considerable efforts have been made to utilize agricultural and forest residues as biomass feedstock for the production of second-generation bioethanol as an alternative fuel. Fermentation utilizing strains of Zymomonas mobilis and the use of simultaneous saccharification and fermentation (SSF) process has been proposed. Statistical experimental design was used to optimize the conditions of SSF, evaluating solid content, enzymatic load, and cell concentration. The optimum conditions were found to be solid content (30%), enzymatic load (25 filter paper units/g), and cell concentration (4 g/L), resulting in a maximum ethanol concentration of 60 g/L and a volumetric productivity of 1.5 g L^?1?h^?1.     

Ethanol Production from the Organic Fraction Obtained After Thermal Pretreatment of Municipal Solid Waste

In this work, the use of organic fraction from municipal solid waste (MSW) as substrate for ethanol production based on enzymatic hydrolysis was evaluated. MSW was subjected to a thermal pretreatment (active hygienization) at 160?°C from 5 to 50 min. The organic fiber obtained after 30 min was used as substrate in a simultaneous saccharification and fermentation (SSF) and fed-batch SSF process using cellulases and amylases. In a fed-batch mode with 25% (w/w) substrate loading, final ethanol concentration of 30 g/L was achieved (60% of theoretical). In these conditions, more than 160 L of ethanol per ton of dry matter could be produced from the organic fraction of MSW.     

The Influence of Initial Xylose Concentration, Agitation, and Aeration on Ethanol Production by Pichia stipitis from Rice Straw Hemicellulosic Hydrolysate

Rice straw hemicellulosic hydrolysate was used as fermentation medium for ethanol production by Pichia stipitis NRRL Y-7124. Shaking bath experiments were initially performed aiming to establish the best initial xylose concentration to be used in this bioconversion process. In the sequence, assays were carried out under different agitation (100 to 200 rpm) and aeration (V _flask/V _medium ratio varying from 2.5 to 5.0) conditions, and the influence of these variables on the fermentative parameters values (ethanol yield factor, Y _P/S; cell yield factor, Y _X/S; and ethanol volumetric productivity, Q _P) was investigated through a 2² full-factorial design. Initial xylose concentration of about 50 g/l was the most suitable for the development of this process, since the yeast was able to convert substrate in product with high efficiency. The factorial design assays showed a strong influence of both process variables in all the evaluated responses. The agitation and aeration increase caused a deviation in the yeast metabolism from ethanol to biomass production. The best results (Y _P/S?= 0.37 g/g and Q _P?=?0.39 g/l.h) were found when the lowest aeration (2.5 V _flask/V _medium ratio) and highest agitation (200 rpm) levels were employed. Under this condition, a process efficiency of 72.5% was achieved. These results demonstrated that the establishment of adequate conditions of aeration is of great relevance to improve the ethanol production from xylose by Pichia stipitis, using rice straw hemicellulosic hydrolysate as fermentation medium.     

The Operable Modeling of Simultaneous Saccharification and Fermentation of Ethanol Production from Cellulose

An operable batch model of simultaneous saccharification and fermentation (SSF) for ethanol production from cellulose has been developed. The model includes four ordinary differential equations that describe the changes of cellobiose, glucose, yeast, and ethanol concentrations with respect to time. These equations were used to simulate the experimental data of the four main components in the SSF process of ethanol production from microcrystalline cellulose (Avicel PH101). The model parameters at 95% confidence intervals were determined by a MATLAB program based on the batch experimental data of the SSF. Both experimental data and model simulations showed that the cell growth was the rate-controlling step at the initial period in a series of reactions of cellulose to ethanol, and later, the conversion of cellulose to cellobiose controlled the process. The batch model was extended to the continuous and fed-batch operating models. For the continuous operation in the SSF, the ethanol productivities increased with increasing dilution rate, until a maximum value was attained, and rapidly decreased as the dilution rate approached the washout point. The model also predicted a relatively high ethanol mass for the fed-batch operation than the batch operation.     

An Improved Process of Ethanol Production from Hemicellulose: Bioconversion of Undetoxified Hemicellulosic Hydrolyzate from Steam-Exploded Corn Stover with a Domesticated Pichia stipitis

Bioconversion of undetoxified hemicellulosic hydrolyzate from steam-exploded corn stover was investigated with a domesticated Pichia stipitis CBS 5776. The countercurrent washing was applied to recover sugars from the steam-exploded corn stover, which could enrich sugars in washing liquor and give an efficient saving of water. Acid concentration, reaction temperature, and time were optimized for the acid post-hydrolysis of oligosaccharides in steam-exploded prehydrolyzate by a central composite design and response surface methodology. The domestication of P. stipitis to the hydrolyzate resulted in improving sugar consumption and ethanol yield by gradually increasing the ratio of hydrolyzate in the medium. Recycling utilization of the domesticated yeast demonstrated that the yeast kept a stable ability of fermenting both hexose and pentose in the undetoxified hydrolyzate. The sugar consumption and ethanol yield were over 90 and 80?%, respectively.     

Ethanol Production from Cashew Apple Bagasse: Improvement of Enzymatic Hydrolysis by Microwave-Assisted Alkali Pretreatment

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.     

Production of Lactic Acid from Sucrose: Strain Selection, Fermentation, and Kinetic Modeling

Lactic acid is an important product arising from the anaerobic fermentation of sugars. It is used in the pharmaceutical, cosmetic, chemical, and food industries as well as for biodegradable polymer and green solvent production. In this work, several bacterial strains were isolated from industrial ethanol fermentation, and the most efficient strain for lactic acid production was selected. The fermentation was conducted in a batch system under anaerobic conditions for 50 h at a temperature of 34 °C, a pH value of 5.0, and an initial sucrose concentration of 12 g/L using diluted sugarcane molasses. Throughout the process, pulses of molasses were added in order to avoid the cell growth inhibition due to high sugar concentration as well as increased lactic acid concentrations. At the end of the fermentation, about 90% of sucrose was consumed to produce lactic acid and cells. A kinetic model has been developed to simulate the batch lactic acid fermentation results. The data obtained from the fermentation were used for determining the kinetic parameters of the model. The developed model for lactic acid production, growth cell, and sugar consumption simulates the experimental data well.     

Fermentation of Biologically Pretreated Wheat Straw for Ethanol Production: Comparison of Fermentative Microorganisms and Process Configurations

The pretreatment of lignocellulosic biomass with white-rot fungi to produce bioethanol is an environmentally friendly alternative to the commonly used physico-chemical processes. After biological pretreatment, a solid substrate composed of cellulose, hemicellulose and lignin, the two latter with a composition lower than that of the initial substrate, is obtained. In this study, six microorganisms and four process configurations were utilised to ferment a hydrolysate obtained from wheat straw pretreated with the white-rot fungus Irpex lacteus. To enhance total sugars utilisation, five of these microorganisms are able to metabolise, in addition to glucose, most of the pentoses obtained after the hydrolysis of wheat straw by the application of a mixture of hemicellulolytic and cellulolytic enzymes. The highest overall ethanol yield was obtained with the yeast Pachysolen tannophilus. Its application in combination with the best process configuration yielded 163 mg ethanol per gram of raw wheat straw, which was between 23 and 35 % greater than the yields typically obtained with a conventional bioethanol process, in which wheat straw is pretreated using steam explosion and fermented with the yeast Saccharomyces cerevisiae.     

Continuous Succinic Acid Fermentation by Actinobacillus Succinogenes: Assessment of Growth and Succinic Acid Production Kinetics

Applied Biochemistry and Biotechnology - Succinic acid is one of the most interesting platform chemicals that can be produced in a biorefinery approach. The paper reports the characterization of...     

Biotechnological Production of Phenyllactic Acid and Biosurfactants from Trimming Vine Shoot Hydrolyzates by Microbial Coculture Fermentation

Coculture fermentations show advantages for producing food additives from agroindustrial wastes, considering that different specified microbial strains are combined to improve the consumption of mixed sugars obtained by hydrolysis. This technology dovetails with both the growing interest of consumers towards the use of natural food additives and with stricter legislations and concern in developed countries towards the management of wastes. The use of this technology allows valorization of both cellulosic and hemicellulosic fractions of trimming vine shoots for the production of lactic acid (LA), phenyllactic acid (PLA), and biosurfactants (BS). This work compares the study of the potential of hemicellulosic and cellulosic fractions of trimming vine shoots as cheaper and renewable carbon sources for PLA and BS production by independent or coculture fermentations. The highest LA and PLA concentrations, 43.0 g/L and 1.58 mM, respectively, were obtained after 144 h during the fermentation of hemicellulosic sugars and simultaneous saccharification and fermentation (SSF) carried out by cocultures of Lactobacillus plantarum and Lactobacillus pentosus. Additionally, cell-bond BS decreased the surface tension (ST) in 17.2 U; meanwhile, cell-free supernatants (CFS) showed antimicrobial activity against Salmonella enterica and Listeria monocytogenes with inhibition halos of 12.1?±?0.6 mm and 11.5?±?0.9 mm, respectively.     

Efficient Production of Ethanol from Empty Palm Fruit Bunch Fibers by Fed-Batch Simultaneous Saccharification and Fermentation Using Saccharomyces cerevisiae

The concentration of ethanol produced from lignocellulosic biomass should be at least 40 g l^?1 [about 5 % (v/v)] to minimize the cost of distillation process. In this study, the conditions for the simultaneous saccharification and fermentation (SSF) at fed-batch mode for the production of ethanol from alkali-pretreated empty palm fruit bunch fibers (EFB) were investigated. Optimal conditions for the production of ethanol were identified as temperature, 30 °C; enzyme loading, 15 filter paper unit g^?1 biomass; and yeast (Saccharomyces cerevisiae) loading, 5 g l^?1 of dry cell weight. Under these conditions, an economical ethanol concentration was achieved within 17 h, which further increased up to 62.5 g l^?1 after 95 h with 70.6 % of the theoretical yield. To our knowledge, this is the first report to evaluate the economic ethanol production from alkali-pretreated EFB in fed-batch SSF using S. cerevisiae.     

酸预处理对酶法骨明胶功能性质和分子质量分布的影响

本文以牛骨粉为原料,采用酶解法制备明胶,考察了骨粉预处理试剂——盐酸的浓度对明胶产品的冻力、粘度、分子量分布和等电点的影响.研究表明,随着骨粉预处理用的盐酸浓度的增大,明胶产率降低.骨粉经过盐酸预处理后,明胶产品的冻力大于300 bloom g,高于原料未经盐酸处理得到的明胶产品.与传统的碱法工艺明胶相比,酶法明胶具有高冻力、高等电点和相对较低的粘度等特点.采用聚丙烯酰胺凝胶电泳表征明胶的分子质量分布,酶法明胶不但具有传统碱法明胶具有的96 KDa、97 KDa、193 KDa和289 KDa组分,而且具有165 KDa和120 KDa组分.酶法明胶的等电点在碱性范围内,随着预处理用盐酸浓度的增大,明胶产品的等电点升高.骨料的预处理工艺对明胶的产率、冻力、粘度、等电点和分子质量分布有重要的影响,在明胶制备过程中,通过调控骨料预处理酸浓度可以调控明胶的技术指标.     

Integrated Use of Residues from Olive Mill and Winery for Lipase Production by Solid State Fermentation with Aspergillus sp.

Two-phase olive mill waste (TPOMW) is presently the major waste produced by the olive mill industry. This waste has potential to be used as substrate for solid state fermentation (SSF) despite of its high concentration of phenolic compounds and low nitrogen content. In this work, it is demonstrated that mixtures of TPOMW with winery wastes support the production of lipase by Aspergillus spp. By agar plate screening, Aspergillus niger MUM 03.58, Aspergillus ibericus MUM 03.49, and Aspergillus uvarum MUM 08.01 were chosen for lipase production by SSF. Plackett–Burman experimental design was employed to evaluate the effect of substrate composition and time on lipase production. The highest amounts of lipase were produced by A. ibericus on a mixture of TPOMW, urea, and exhausted grape mark (EGM). Urea was found to be the most influent factor for the lipase production. Further optimization of lipase production by A. ibericus using a full factorial design (3²) conducted to optimal conditions of substrate composition (0.073 g urea/g and 25 % of EGM) achieve 18.67 U/g of lipolytic activity.     

Improved Ethanol Production by Mixed Immobilized Cells of Kluyveromyces marxianus and Saccharomyces cerevisiae from Cheese Whey Powder Solution Fermentation

Ethanol productions from cheese whey powder (CWP) solution were investigated by using free or immobilized cells of Kluyveromyces marxianus in monocultures or mixed cultures with free or immobilized cells of K. marxianus and Saccharomyces cerevisiae. K. marxianus free cells produced 3.8% v/v ethanol in monocultures, while S. cerevisiae immobilized cells produced 5.3% v/v ethanol in mixed cultures. The percentage of theoretical yield was found to be higher in mixed cultures than that in monocultures. The maximum ethanol fermentation efficiency was achieved (79.9% of the theoretical value) using mixed cultures of immobilized cells of K. marxianus and S. cerevisiae. The beads were relatively stable without significant reduction in activity for about eight batches of fermentation.     

Synthesis of Allobetulin, 28-Oxyallobetulin and Related Biomarkers from Betulin and Betulinic Acid Catalysed by Solid Acids

Betulin (1a) is an abundant natural product in the birch bark. Betulin itself currently has little usage. However, allobetulin (2a) has been used as an important intermediate in the further transformation of triterpenoids and as a sample for biological studies.¹ For example, allobetulin was further transformed to a highly active antifeedant for heliothis zea larvae. Some biomarkers (3a,b; 4a,b) with the same or similar structure as ring-E of 2a were identified in a brown coal.³ Consequently, the conversion of 1a to synthetically, biologically and geochemically more important 2a is of great significance. The transformation of 1a to 2a was reported as early as 1922 by Schulze et al in which betulin was isomerized by formic acid, involving formation and hydrolysis of allobetulin formate, to give 2a in moderate yield.⁴     

Aluminum Oxide Coated Cellulose Fibers Modified with n-Propylpyridinium Chloride Silsesquioxane Polymer: Preparation, Characterization, and Adsorption of Some Metal Halides from Ethanol Solution

Aluminum oxide coated cellulose fibers were modified, by an impregnation procedure, with n-propylpyridinium chloride silsesquioxane polymer. Good adherence of the polymer to the surface of modified cellulose fibers was obtained due to the Al-O-Si bond formation. The metal X-ray mapping showed that aluminum oxide and the silsequioxane polymer (Al and Si mapping) are highly dispersed on the fiber's surface. The ion exchange capacity of the material, determined on basis of exchangeable chloride ions, was 1.1 mmol g-1. The adsorption isotherms of FeCl3, CuCl2, and ZnCl2 from ethanol solutions were determined for each metal. The adsorption capacities were (in mmol g-1): FeCl3 = 0.82, CuCl2 approximately ZnCl2 = 0.37. The metal ions are adsorbed as anionic complex species by the following equilibrium reaction: + MCln right arrow over left arrow Copyright 1999 Academic Press.     

Adding Value to the Oil Cake as a Waste from Oil Processing Industry: Production of Lipase and Protease by <Emphasis Type="Italic">Candida utilis</Emphasis> in Solid State Fermentation

Olive oil cake is a by-product from the olive oil processing industry and can be used for the lipase and protease production by Candida utilis in solid state fermentation. Different carbon and nitrogen sources were evaluated, and the results showed that the supplementation of the substrate with maltose and starch as carbon sources and yeast extract as a nitrogen source significantly increased the lipase production. The best results were obtained with maltose, whereas rather low lipase and protease activities were found with glucose and oleic acid. Response surface methodology and a five-level–three-factor central composite rotatable design were used to evaluate the effects of the initial moisture content, inoculum size and fermentation time on both lipase and protease activity levels. A lipase activity value of ≈25 U g^-1 and a protease activity value of 110 U g^-1 were obtained under the optimized fermentation conditions. An alkaline treatment of the substrate appeared to be efficient, leading to increases of 39% and 133% in the lipase and protease production, respectively. The results showed that the olive cake could be a good source for enzyme production by solid state fermentation.     

Production,Purification and Characterisation of a Potential Fibrinolytic Protease from Endophytic <Emphasis Type="Italic">Xylaria curta</Emphasis> by Solid Substrate Fermentation

The present investigation highlights the optimal conditions for production of a non-toxic, bi-functional fibrinolytic enzyme xylarinase produced by endophytic fungus Xylaria curta by solid substrate fermentation using rice chaff medium. The purified enzyme is a monomeric protein with a molecular mass of ～33 kDa. The enzyme exhibits cleavage of Aα and Bβ chains of fibrin(ogen) and has no effect on γ chain. The optimal fibrinolytic activity of the enzyme was observed at 35 °C and pH 8. The fibrinolytic activity was enhanced in the presence of Ca²⁺, whereas it was completely inhibited in the presence of Fe²⁺ and Zn²⁺ ions and inhibitors like EDTA and EGTA suggesting it to be a metalloprotease. The K _m and V _max of the enzyme for azocasein were 326 μM and 0.13 μM min^?1. The N-terminal sequence of the enzyme (SNGPLPGGVVWAG) was same when compared to xylarinase isolated from culture broth of X. curta. Thus, xylarinase could be exploited as a potent clot busting enzyme which could be produced on large scale using solid substrate fermentation.     

气相色谱法测定丙烯氧化生产丙烯酸尾气中丙烯醛、乙酸、丙烯酸含量

采用毛细管气相色谱法测定丙烯氧化生产丙烯酸尾气中丙烯醛、乙酸、丙烯酸的含量,色谱柱为FFAP(30m×0.53 mm,1μm),检测器为FID,用外标法进行定量,尾气样品中丙烯醛、乙酸、丙烯酸的检出限分别为0.025,0.033,0.031 mg/m3,测定结果的相对偏差为0.97%~2.63%(n=5),加标回收率为98.29%~103.60%。