Kinetics Of Cellulose Degradation Research Articles

Kinetics of cellulose degradation in bamboo paper

Abstract In this article, the chain scission kinetics of cellulose in acid bamboo paper aging were studied and further applied to evaluate the lifespan of acid bamboo paper. In combination with analytical theory and Monte-Carlo simulations, the ideal random scission mechanism of cellulose macromolecules with arbitrary molecular weight distribution (MWD) was studied first. The molecular weight distribution evolutions obtained by the two methods were in good agreement, indicating the feasibility of the Monte-Carlo algorithm. Furthermore, the relationship between the ideal random scission mechanism and real paper aging was studied in an accelerated aging experiment at 105 °C. The Monte-Carlo algorithm could basically reproduce the MWD of accelerated aging at various degradation degrees, indicating that the ideal random scission mechanism is predominant in bamboo paper aging. Therefore, the relevant kinetic model can be applied to lifespan evaluation. In three other aging experiments, the activation energy of paper aging was determined by the Arrhenius equation, which facilitated the calculation of the rate constant of paper aging at room temperature. It is expected that bamboo paper can be preserved for more than a thousand years.

Comprehensive thermokinetic modelling and predictions of cellulose decomposition in isothermal, non-isothermal, and stepwise heating modes

The increasing significance of biomass in attaining ultimate sustainability in a multitude of vectors demands a deeper understanding of its underlying components. The pyrolytic breakdown of cellulose, a major biomass component, has been a subject of intense research since the 1950 s, and despite significant research carried out and published thus far, the kinetics of cellulose degradation continue to be a source of debate. Herein, this work investigates the pyrolytic degradation of cellulose using Advanced Kinetics and Technology Solutions (AKTS) software. Kinetic parameters were computed using three methods, Friedman’s differential iso-conversional, FWO and ASTM-E698. The results indicate Ea values of 40–181, 68–166, and 152.1 kJ/mol, using Friedman’s, FWO and ASTM-E698 methods, respectively. Based on the results obtained via Friedman’s differential iso-conversional method, predictions under isothermal, non-isothermal and stepwise heating profiles are presented. The predictions revealed that rapid degradation takes place up to 80% conversion, and a temperature of 350–400 °C is required to efficiently achieve this, while temperatures of 650 °C and higher are needed to efficiently achieve a 100% conversion in less than 2 h, under isothermal conditions.

The Effects of Natural Dye and Iron Gall Ink on Degradation Kinetics of Cellulose by Accelerated Ageing

ABSTRACT Iron gall inks have a destructive effect on paper supports due to their acidic and transition metal-containing nature. For the chemical stabilization of paper-based objects, conservation studies include both antioxidant and deacidification treatments. In order to evaluate the effectiveness of the treatments, accelerated ageing experiments are performed and changes during ageing are measured. Historical manuscripts may contain colored papers and since only natural dyes and pigments were available until the development of modern chemistry in the nineteenth century, the palette was limited. Organic dyes mainly consisted of colourants obtained from plants and insects. In this study, colored papers of manuscripts from the fifteenth century which belong to the collections of Millet Library, İstanbul were analyzed via high-performance liquid chromatography. According to the results, model papers were dyed with Rheum ribes L. (rhubarb), and then an iron gall ink, prepared according to a historical recipe, was applied to them. Due to acid and transition metal content, a stabilization treatment including alkali and an antioxidant was applied on a set of samples and after 12 days of accelerated ageing, changes in pH, degree of polymerization, and optical properties of the samples were monitored. A viscometer, a useful tool to monitor the efficiency of a treatment, was employed for the determination of degree of polymerization values. Data obtained from viscometric measurements were used to evaluate the degradation rate constants of the samples. Comparison of rate constants showed that treatment had a beneficial effect.

Characteristics and Kinetics of Cellulose Degradation in Oil-Impregnated Pressboard under Simultaneous Thermal-Electrical-Mechanical Stress Accelerated Aging

This study aims to investigate the characteristics and kinetics of cellulose degradation in oil-impregnated pressboard (OIP) under simultaneous thermal-electrical-mechanical stress accelerated aging. Thus, the multi-stress aging experimental setup is designed and established. OIP multi-stress aging experiments are performed at 130 °C, a DC electric voltage of +6 kV, vibration amplitude of 10-50 μm and vibration frequency of 100-300 Hz. The aging characteristics of pressboard and oil are then measured, including the degree of polymerization and aging by-products (i.e., furfural, moisture, acidity and dissolved gas). Investigations on aging characteristics reveal that thermal stress is still the dominant factor of cellulose degradation, while electrical and mechanical stresses serve as aging acceleration factors. The simultaneous thermal-electrical-mechanical aging of OIP is 10-24% faster than the single thermal aging. Moreover, the kinetics of cellulose degradation is also proposed to predict the bond scission fraction of cellulose with a goodness-of-fitting over 0.97. Finally, the correlations between the parameters in the kinetics of cellulose degradation and mechanical stress reveal that the increase of vibration amplitude generates more weak and amorphous links available for degradation, while the increase of vibration frequency accelerates the reaction rate.

Studies on thermal and degradation kinetics of cellulose micro/nanoparticle filled polylactic acid (PLA) based nanocomposites

The aim of this work is to understand the effect of concentration of plasticizer, particle size and wt% of nanoparticles on nanocomposites by fabricating poly lactic acid (PLA) based bio-nanocomposites. The bio-nanocomposites were prepared by a solution casting method with PLA as the matrix, chloroform as solvent and poly ethylene glycol (PEG) as plasticizer. Microcrystalline cellulose (MCC) and cellulose nanocrystal (CNC) were used as reinforcements in 1, 3 and 5 wt% to modify the properties of the bio-nanocomposite. The degradation kinetics of the PLA based composites were determined by using the Coats-Redfern equation over the range of 0-5 wt% of MCC and CNC. Fabricated PLA based composite films were analyzed by differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and field emission scanning electron microscopy (FE-SEM). The analyses showed that the amount of PEG, MCC and CNC affected the degree of crystallinity. DSC results showed that the MCC/CNC content level affected the degree of crystallinity compared to neat PLA. The FTIR showed a free hydroxyl group (−OH) present in the system. The TGA analysis showed that the PLA/MCC3%/ PEG 10% composition had the highest stability compared to the other compositions but less than neat PLA.

Performance improvement of sediment microbial fuel cell by enriching the sediment with cellulose: Kinetics of cellulose degradation

Abstract A sediment microbial fuel cell (SMFC) could offer sustainable solution for bio-remediation of aquaculture used water to maintain favorable condition for fishes and simultaneously can produce bio-electricity. In this study, the performance of the SMFC was enhanced by enriching the sediment using cellulose at the rate of 4 wt. % and 6 wt. % by making SMFC-2 and SMFC-3, respectively. The SMFCs were operated in closed circuit (300 Ω , external resistance) and open circuit mode ( ∞ Ω , external resistance) denoted by SMFC-2C, SMFC-3C, SMFC-2O and SMFC-3O respectively. The control, SMFC- 1 was operated without addition of cellulose in sediment in closed circuit mode only. Degradation kinetics of cellulose in SMFCs was evaluated using modified logistic model. In terms of bio-electricity generation, power density was found to be highest in SMFC-3 (7.29 mWm−2 and 6.51 mWm−2 in close and open circuit mode, respectively), followed by SMFC-2C (5.91 mWm−2), 2O (5.18 mWm−2) and SMFC-1 (4.23 mWm−2). All the SMFCs have shown sufficient chemical oxygen demand removal efficiency varied from 70 to 91%. Maximum degradation rate of cellulose was noted to be 1.69, 2.17, 1.89, 0.99 and 0.99 mg. g−1.d−1 for SMFC-1, SMFC-2C, SMFC-2O, SMFC-3C and SMFC-3O respectively.

Series solution of the autocatalytic hydrolysis of cellulose

The chemical degradation kinetics of cellulose is of scientific interest, as well as its practical importance in many industrial activities for optimal design. Much work has been done recently to understand the depolymerizaton of cellulose in homogeneous acidic medium on the assumption of autocatalytic hydrolysis with a positive feedback of acid production from the degraded biopolymer. Series solutions are obtained for concentrations of cellulose chains and degraded cellulose chains by Taylor series and variational iteration method. Depolymerization of cellulose strongly depends upon the initial conditions, and the concentration of cellulose chains changes exponentially with a linear and square/cubic time dependence. The analytical solution can be used for optimal design of the degradation process.

Influence of cellulose polymerization degree and crystallinity on kinetics of cellulose degradation

Cellulose was treated in ethylene glycol with p-toluene sulfonic acid monohydrate as a catalyst at different temperatures. At the highest treatment temperature (150 °C) liquefaction of wood pulp cellulose was achieved and was dependant on cellulose polymerization degree (DP). Furthermore, the rate of amorphous cellulose weight loss was found to increase with cellulose degree of polymerization, while the rate of crystalline cellulose weight loss was reciprocal to the size of the crystallites. The cellulose degradation was studied by monitoring of the molecular mass decrease by size-exclusion chromatography. It was revealed that microcrystalline cellulose degrades via a ‘quantum mode’ mechanism, while the degradation of Whatman filter paper no 1. and cotton linters proceeded randomly and were partly dependent on the starting polymerization degree, crystallinity, and treatment temperature. The kinetics of cellulose degradation in heterogeneous media was described by means of a one-stage model, characterised by the consumption of glycosidic bonds in amorphous and crystalline cellulose regions until the levelling-off degree of polymerization is reached.

Materials produced from plant biomass: part II: evaluation of crystallinity and degradation kinetics of cellulose

In this study Eucalyptus grandis (CEG) and Pinus taeda (CPT) cellulose fibers obtained from kraft and sulfite pulping process, respectively, were characterized using Fourier transform infrared (FTIR) spectroscopy and thermogravimetry (TGA). The degradation kinetic parameters were determined by TGA using Coats and Redfern method. FTIR results showed that CPT presented a more ordered structure with higher crystallinity than CEG. Thermogravimetric results showed that CPT had a higher thermal stability than CEG. The kinetic results revel that for CEG the degradation mechanism occurs mainly by random nucleation, although phase boundary controlled reactions also occurs while for CPT the degradation process is more related with phase boundary controlled reactions. Results demonstrated that differences between thermal stability and degradation mechanisms might be associated with differences in the cellulose crystalline structure probably caused by different pulping processes used for obtaining the cellulose fibers.

Modeling Microbial Dynamics in Heterogeneous Environments: Growth on Soil Carbon Sources

We have developed a new kinetic model to study how microbial dynamics are affected by the heterogeneity in the physical structure of the environment and by different strategies for hydrolysis of polymeric carbon. The hybrid model represented the dynamics of substrates and enzymes using a continuum representation and the dynamics of the cells were modeled individually. Individual-based biological model allowed us to explicitly simulate microbial diversity, and to model cell physiology as regulated via optimal allocation of cellular resources to enzyme synthesis, control of growth rate by protein synthesis capacity, and shifts to dormancy. This model was developed to study how microbial community functioning is influenced by local environmental conditions in heterogeneous media such as soil and by the functional attributes of individual microbes. Microbial community dynamics were simulated at two spatial scales: micro-pores that resemble 6-20-μm size portions of the soil physical structure and in 111-μm size soil aggregates with a random pore structure. Different strategies for acquisition of carbon from polymeric cellulose were investigated. Bacteria that express membrane-associated hydrolase had different growth and survival dynamics in soil pores than bacteria that release extracellular hydrolases. The kinetic differences suggested different functional niches for these two microbe types in cellulose utilization. Our model predicted an emergent behavior in which co-existence of membrane-associated hydrolase and extracellular hydrolases releasing organisms led to higher cellulose utilization efficiency and reduced stochasticity. Our analysis indicated that their co-existence mutually benefits these organisms, where basal cellulose degradation activity by membrane-associated hydrolase-expressing cells shortened the soluble hydrolase buildup time and, when enzyme buildup allowed for cellulose degradation to be fast enough to sustain exponential growth, all the organisms in the community shared the soluble carbon product and grew together. Although pore geometry affected the kinetics of cellulose degradation, the patterns observed for the bacterial community dynamics in the 6-20 μm-sized micro-pores were relevant to the dynamics in the more complex 111-μm-sized porous soil aggregates, implying that micro-scale studies can be useful approximations to aggregate scale studies when local effects on microbial dynamics are studied. As shown with examples in this study, various functional niches of the bacterial communities can be investigated using complex predictive mathematical models where the role of key environmental aspects such as the heterogeneous three-dimensional structure, functional niches of the community members, and environmental biochemical processes are directly connected to microbial metabolism and maintenance in an integrated model.

Effect of microaerobic conditions on the degradation kinetics of cellulose

Limited oxygen supply to sludge digesters has shown to be an effective method to eliminate hydrogen sulfide from the biogas produced during anaerobic digestion but uneven results have been found in terms of the effect on the degradation of complex organic matter. In this study, the effect that the limited oxygen supply provoked on the “anaerobic” degradation of cellulose was evaluated in batch-tests. The microaerobic assays showed to reach a similar maximum production of methane than the anaerobic ones after 19d and a similar hydrolytic activity (considering a first order rate constant); however, the microaerobic assays presented a shorter lag-phase time than the anaerobic test resulting in faster production of methane during the first steps of the degradation; specifically, the maximum methane production found in the anaerobic test in 19d was found in the microaerobic test before the day 15.

Quantitative Assessment of the Enzymatic Degradation of Amorphous Cellulose by Using a Quartz Crystal Microbalance with Dissipation Monitoring

The systematic evaluation of the degradation of an amorphous cellulose film by a monocomponent endoglucanase (EG I) by using a quartz crystal microbalance with dissipation monitoring (QCM-D) identified several important aspects relevant to the study the kinetics of cellulose degradation by enzymes. It was demonstrated that, to properly evaluate the mechanism of action, steady state conditions in the experimental set up need to be reached. Rinsing or diluting the enzyme, as well as concentration of the enzyme, can have a pronounced effect on the hydrolysis. Quantification of the actual hydrolysis was carried out by measuring the film thickness reduction by atomic force microscopy after the enzymatic treatment. The values correlated well with the frequency data obtained by QCM-D measurement for corresponding films. This demonstrated that the evaluation of hydrolysis by QCM-D can be done quantitatively. Tuning of the initial thickness of films enabled variation of the volume of substrate available for hydrolysis which was then utilized in establishing a correlation between substrate volume and hydrolytic activity of EG I as measured by QCM-D. It was shown that, although the amount of substrate affects the absolute rate of hydrolysis, the relative rate of hydrolysis does not depend on the initial amount of substrate in steady state system. With this experimental setup it was also possible to demonstrate the impact of concentration on crowding of enzyme and subsequent hydrolysis efficiency. This effort also shows the action of EG I on a fully amorphous substrate as observed by QCM-D. The enzyme was shown to work uniformly within the whole volume of swollen film, however being unable to fully degrade the amorphous film.

On the kinetics of cellulose degradation: looking beyond the pseudo zero order rate equation

The kinetics of cellulose degradation was analysed by means of a two-stage model, characterised by an autoretardant and autocatalytic regime, later tempered by the consumption of glycosidic bonds in the amorphous regions. The proposed model explains the effects on the kinetic equations of different modes of ageing (acid hydrolysis, ageing in ventilated oven or sealed vessels), initial oxidation of cellulose and experimental procedures (with or without reduction of oxidised groups). The autoretardant branch can be analysed in a quantitative way, while the integration of the non-linear autocatalytic branch is allowed in some cases, characterised by the decrease of pH and/or emission of acid volatile organic compounds (VOCs). Most of the controversial results of the literature can be easily explained, but the proposed model offers also a guide for further studies on the kinetics of cellulose degradation.

The Influence of Levelling-off Degree of Polymerisation on the Kinetics of Cellulose Degradation

The Influence of Levelling-off Degree of Polymerisation on the Kinetics of Cellulose Degradation

Characterization of a spontaneous adhesion-defective mutant of Ruminococcus albus strain 20.

A spontaneous adhesion-defective mutant (mutant D5) of Ruminococcus albus strain 20 was isolated and compared to the parent to investigate the impact of the mutation on cellulolysis and to identify the adhesion mechanism of R. albus. The comparison of kinetics of cellulose degradation by strain 20 and mutant D5 showed that the mutation delayed and reduced bacterial growth on cellulose and cellulose degradation. These results were partly explained by a twofold lower cellulase activity in the mutant than in the parent. The glycocalyx of strain 20, observed by transmission electron microscopy, was large and homogeneous, and linked cells to cellulose. The mutant glycocalyx was aggregated at its periphery and cells attached loosely to cellulose. A glycoprotein of 25 kDa (GP25), present in the membrane fraction and the extracellular medium of strain 20, was not detected in the same fractions of mutant D5. Though glycoprotein GP25 did not bind to cellulose, it may be involved in adhesion as an intermediate component. Different cell-surface features of mutant D5 (cellulases, glycoprotein GP25, glycocalyx) were thus affected, any or all of which may be involved in its adhesion-defective phenotype. These results suggest that adhesion and cellulolysis are linked and that adhesion is a multifactorial phenomenon that involves at least the extracellular glycocalyx.

An investigation of the kinetics of cellulose degradation under non-isothermal conditions

The degree of polymerization (DP) of a polymer system subjected to non-isothermal depolymerization is examined kinetically with a preliminary application to the study of cellulose degradation. An equation for the time dependence of the DP observed under non-isothermal degradation using a linear temperature ramp is derived from the relevant isothermal kinetic equations. An iterative computerbased method of fitting non-isothermal degree of polymerization (NIDP) data is also presented. The activation energy and the Arrhenius A-factor associated with the depolymerization process can be varied independently to achieve an optimized fit to experimental NIDP data and may be used to calculate the predicted lifetime of the polymer in service. The potential of NIDP data analysis to quickly deliver these kinetic parameters is identified and the confidence ranges in the predicted lifetimes derived from NIDP data analyses appear to be similar to those derived from isothermal analyses of DP data. Experimental NIDP data support the notion that the prolonged degradation of cellulose does not produce oligomers of DP much less than ca. 200.

Use of continuous‐culture techniques for determining the growth kinetics of a celluloytic Thermoactinomyces sp.

AbstractIn order to better understand the kinetics of cellulose degradation by Thermoactinomyces sp., continuous‐culture experiments were performed utilizing the various intermediates of cellulose degradation as the feed substrates. Steady‐state data from the glucose runs suggest that this organism has a growth yield of 0.42 g cell/g glucose, and a specific maintenance of 0.24 g glucose/g cell/hr. The Monod equation did not seen to model the growth well, since a plot of 1/D vs. 1/S gave a maximum specific growth rate that was even lower than one of the steady‐state dilution rates. A dynamic washout experiment suggested a maximum specific specific growth rate of 0.36 hr−1 and indicated that glucose is only slightly growth inhibitory as the inhibition constant, Ki, is 19 g glucose/liter. An equation for substrate concentration for washout conditions was derived. This equation predicted the transient glucose concentration relatively well. A fill‐and‐draw technique was investigated for determination of the growth parameters. It was not successful because of difficulties in contamination and accurately monitoring the dissolved oxygen in the small highly agitated vessel. However, the technique could be useful in studying the growth characteristics of sludge in a waste treatment system where contamination is not a worry. One could cover the medium surface and use a nonsterilizable dissolved oxygen probe of high sensitivity membrane to overcome these difficulties.