Weak Acid Hydrolysis Research Articles

Weak acid hydrolysis strategy to oxygen vacancy enriched BiOBrnI1-n nanosheet for photodegrading various contaminants

BiOBrnI1-n solid solution enriched with oxygen vacancies (OVs) was obtained using simple hydrolysis method and exhibited excellent ability to remove various contaminants, inclusive of bisphenol A (BPA), rhodamine B (RhB), methyl orange (MO), tetracycline hydrochloride (TCH) and sulfamethazine (SMT). The photocatalytic degradation efficiency of optimal BiOBrnI1-n catalyst for BPA is 128 and 13.8 times higher than that of BiOBr and BiOI, respectively. The excellent degradation activity benefits from the suitable energy band potential, interior electric field and superior charge separation efficiency. The test of catalytic cycles confirms the high reusability of BiOBrnI1-n. Photoinduced h+, ·O2−, and e− serve as reactive species in the degradation process. This work provides an effective photocatalyst for the photodegradation of various contaminants.

Development of an Integrated Bioprocess System for Bioethanol and Arabitol Production from Sugar Beet Cossettes.

An innovative integrated bioprocess system for bioethanol production from raw sugar beet cossettes (SBC) and arabitol from remaining exhausted sugar beet cossettes (ESBC) was studied. This integrated three-stage bioprocess system is an example of the biorefinery concept to maximise the use of raw SBC for the production of high value-added products such as sugar alcohols and bioethanol. The first stage of the integrated bioprocess system was simultaneous sugar extraction from SBC and its alcoholic fermentation to produce bioethanol in an integrated bioreactor system (vertical column bioreactor and stirred tank bioreactor) containing a high-density suspension of yeast Saccharomyces cerevisiae (30 g/L). The second stage was the pretreatment of ESBC with dilute sulfuric acid to release fermentable sugars. The resulting liquid hydrolysate of ESBC was used in the third stage as a nutrient medium for arabitol production by non-Saccharomyces yeasts (Spathaspora passalidarum CBS 10155 and Spathaspora arborariae CBS 11463). The obtained results show that the efficiency of bioethanol production increased with increasing temperature and prolonged residence time in the integrated bioreactor system. The maximum bioethanol production efficiency (87.22 %) was observed at a time of 60 min and a temperature of 36 °C. Further increase in residence time (above 60 min) did not result in the significant increase of bioethanol production efficiency. Weak acid hydrolysis was used for ESBC pretreatment and the highest sugar yield was reached at 200 °C and residence time of 1 min. The inhibitors of the weak acid pretreatment were produced below bioprocess inhibition threshold. The use of the obtained liqiud phase of ESBC hydrolysate for the production of arabitol in the stirred tank bioreactor under constant aeration clearly showed that S. passalidarum CBS 10155 with 8.48 g/L of arabitol (YP/S=0.603 g/g and bioprocess productivity of 0.176 g/(L.h)) is a better arabitol producer than Spathaspora arborariae CBS 10155. An innovative integrated bioprocess system for the production of bioethanol and arabitol was developed based on the biorefinery concept. This three-stage bioprocess system shows great potential for maximum use of SBC as a feedstock for bioethanol and arabitol production and it could be an example of a sustainable 'zero waste' production system.

Structural characterization of PCP-Ⅰ from Poria as vaccine adjuvant and its hydrolytic oligosaccharide

Poria is an important medical herb in clinic. The authors isolated a polysaccharide(PCP-Ⅰ) from Poria in previous studies, which is composed of galactose, mannose, fucose and glucose. PCP-Ⅰ exhibited significant adjuvant effects on H1N1 influenza vaccine, hepatitis B surface antigen and anthrax protective antigen, and its adjuvant activity was stronger than aluminium adjuvant. However, little is known about the chemical structure of PCP-Ⅰ at present. In this study, weak acid hydrolysis was used to obtain the backbone oligosaccharide of PCP-Ⅰ. Then periodate oxidation, Smith degradation, methylation analysis, Fourier transform infrared spectroscopy(FT-IR), nuclear magnetic resonance(NMR) and gas chromatography-mass spectrometry(GC-MS) were performed to investigate the chemical structural features of PCP-Ⅰ and its hydrolytic oligosaccharide(PCP-Ⅰ-hy-1). These results suggested that the backbone of PCP-Ⅰ was composed of galactose with α anomeric carbon and β anomeric carbon. The linking residues of galactan are(1→),(l→6) and(1→2,6).

Preparation and characterization of AgNPs@SNC nanocomposites

Starch nanocrystal (SNC) was prepared by 40°C weak sulfuric acid hydrolysis method. Silver nanoparticles (AgNPs) were simply and quickly reduced in situ on starch nanocrystal by ultrasonic assisted reduction method. UV-vis absorption spectrum verified the existence of AgNPs. The surface modification of AgNPs@SNC was carried out by using 3-aminopropyltriethoxysilane (APTES) with simple structure and low cost to improve its dispersivity in the hydrophobic polymer matrix. Then the success of modification was preliminarily confirmed by the Fourier-transform infrared spectroscopy. Taking Staphylococcus aureus and Escherichia coli bacteria as objects of the study, the antibacterial properties of AgNPs@SNC were also explored, and the test results showed that AgNPs@SNC had certain inhibitory effect on Escherichia coli.

Ultrasound-assisted weak-acid hydrolysis of crystalline starch nanoparticles for chemical enhanced oil recovery

Ascorbic acid was used for the first time to synthesize crystalline starch nanoparticles (CSNP). The physical properties of the CSNP were investigated. Rheological properties of the crystalline starch nanofluid (CSNF) were compared with native cassava starch (CS) and commercial polymer xanthan. Interfacial properties of the CSNF at the interface of oil and water (O/W) were investigated at different concentrations and temperatures. Wettability alteration efficiency of CSNF on oil-wet sandstone surface was investigated using the sessile drop method. Core flooding experiment was conducted at reservoir conditions. The methods were effective in producing spherical and polygonal nanoparticles with a mean diameter of 100 nm and increased in crystallinity of 7%. Viscosity increased with increase in surface area and temperature of the CSNF compared to a decrease in viscosity as the temperature increases for xanthan. Interfacial tension (IFT) decreased with increase in concentration of CSNF, electrolyte and temperature. The results show that CSNF can change the wettability of sandstone at low concentration, high salinity and elevated temperature. Pressure drops data shows stability of CSNF at 120 °C. The formation of oil bank was enough to increase oil recovery by 23%.

Synergy of the flow behaviour and disperse phase of cellulose nanoparticles in enhancing oil recovery at reservoir condition.

Ascorbic acid was used for the first time to synthesize cellulose nanoparticles (CNP) extracted from okra mucilage. The physical properties of the CNP including their size distribution, and crystalline structures were investigated. The rheological properties of the cellulose nanofluid (CNF) were compared with the bulk okra mucilage and commercial polymer xanthan. The interfacial properties of the CNF at the interface of oil-water (O/W) system were investigated at different concentrations and temperatures. The effects of the interaction between the electrolyte and ultrasonic were determined. Core flooding experiment was conducted at reservoir condition to justify the effect of the flow behaviour and disperse phase behaviour of CNF on additional oil recovery. The performance of the CNF was compared to conventional EOR chemical. The combined method of ultrasonic, weak-acid hydrolysis and nanoprecipitation were effective in producing spherical and polygonal nanoparticles with a mean diameter of 100 nm, increased yield of 51% and preserved crystallinity respectively. The zeta potential result shows that the CNF was stable, and the surface charge signifies long term stability of the fluid when injected into oil field reservoirs. The CNF, okra and xanthan exhibited shear-thinning and pseudoplastic behaviour. The IFT decreased with increase in concentration of CNF, electrolyte and temperature. The pressure drop data confirmed the stability of CNF at 120°C and the formation of oil bank was enough to increase the oil recovery by 20%. CNF was found to be very effective in mobilizing residual oil at high-temperature high-pressure (HTHP) reservoir condition. The energy and cost estimations have shown that investing in ultrasonic-assisted weak-acid hydrolysis is easier, cost-effective, and can reduce energy consumption making the method economically advantageous compared to conventional methods.

Influence of Ultrasonic on the Flow Behavior and Disperse Phase of Cellulose Nano-particles at Fluid–Fluid Interface

Nano-particles can localize at oil–water (O/W) interface, reduce residual oil saturation, increase the viscosity of brine and decrease the viscosity of crude oil emulsion. However, cost and environmental concerns have limited field application of inorganic, metal and metal oxides nano-particles. In this study, ascorbic acid was used for the first time to synthesize cellulose nano-particles (CNP) extracted from okra mucilage. The physical properties of the CNP including their size distribution and crystalline structures were investigated by transmission electron microscope, dynamic light scattering, Fourier transform infrared spectroscopy and X-ray diffraction. The rheological properties of the cellulose nano-fluid (CNF) were compared with the bulk okra mucilage and commercial polymer xanthan. The interfacial properties of the CNF at the interface of the O/W system were investigated at different concentrations and temperatures. The effect of the interaction between electrolyte and ultrasonic was determined. The combined method of ultrasonic, weak acid hydrolysis and nano-precipitation was effective in producing rod-like and polygonal nano-particles with a mean diameter of 100 nm, increased yield of 51% and preserved crystallinity, respectively. The zeta potential result showed that the CNF is stable, and the surface charge signifies long-term stability of the fluid when injected into oil field reservoirs. From the experimental results, concentration, particle morphology and the surface charge of the solutions were the contributing factors that influenced the rheology of the system. The CNF, okra and xanthan exhibited shear-thinning and pseudo-plastic behavior. The R2 value for the model is very close to unity, indicating that the power-law model describes nearly perfectly the rheological behavior. The consistency index increased as the flow behavior indices decreased with the increase in the concentration. The interfacial tension (IFT) decreased with the increase in concentration of CNF, electrolyte and temperature. Temperature, concentration of CNF and electrolyte were the main factors that influenced the IFT reduction. The results show that investing in ultrasonic-assisted weak acid hydrolysis is easier, cost-effective and can reduce energy consumption making the method economically advantageous compared to conventional methods. The characteristic properties of the CNF suggest that it has potentials to be used to recover trapped oil from pores of reservoirs.

Influence of nanoprecipitation on crystalline starch nanoparticle formed by ultrasonic assisted weak-acid hydrolysis of cassava starch and the rheology of their solutions

In this research, plant and fruits extracts were used for the first time to synthesize crystalline starch nanoparticles (CSNP). The physical properties of the CSNP including their size distribution, crystalline structures were investigated. The isolation, recovery yield and the influence of the process variables were studied. The rheological behaviours of the CSNP were compared and contrasted with the native cassava starch (CS) and commercial polymer xanthan. The combined method of weak-acid hydrolysis, ultrasonic and nanoprecipitation were effective in producing spherical and polygonal nanoparticles with a mean diameter of 100 nm, increased yield of 39% and increased in crystallinity of 7% respectively. The CSNP, CS and xanthan exhibited shear-thinning and pseudoplastic behaviour. The R2 value for the model is very close to unity indicating a perfect fit. Indicating that the power law model best describes the rheological behaviour. Cavitation, nucleation and crystals growth were the dominant mechanism that influenced the formation of CSNP. Whereas, concentration, morphology and the surface charge of the solutions were the main factors that influenced the rheology of the system. The viscosity increased with increase in surface area and temperature of the CS and CSNP in contrast to a decrease in viscosity as the temperature of xanthan increases.

Recovery of glucose from dried distiller's grain with solubles, using combinations of solid-state fermentation and insect culture.

A bioethanol by-product, dried distiller's grains with solubles (DDGS) contains high levels of cellulose and starch. We hypothesized that combinations of solid-state fermentation (SSF) and digestion by black soldier fly larvae (BSFL) (Hermetia illucens) could increase the recovery of glucose from this by-product by concentrating and loosening the cellulose matrix through their activities. DDGS was individually fermented with Aspergillus niger, Aspergillus fumigatus, Trichoderma koningii, Phanerochaete chrysosporium, or Lactobacillus plantarum. The fermented DDGS was fed to BSFL, and glucose recoveries from spent feeds were conducted. SSF increases lipid and protein contents, supporting BSFL growth, and weakens the cellulosic matrix. BSFL use nutrients in SSF-DDGS, further concentrating and weakening the cellulose, i.e., DDGS is halved without changing the cellulose contents. For example, Lactobacillus plantarum SSF with BSFL culture concentrates the cellulose content from 9.7% to 26.5% of spent feed. Glucose recovery was determined using three sequential processes (free glucose determination, weak-acid hydrolysis of amorphous cellulose, and enzymatic hydrolysis of micronized crystalline cellulose). Total glucose obtained from 100 g of DDGS increased from 4.8 to 10.7 g. These results show that the combinations of SSF and BSFL could provide additional fermentable sugars (and insect biomass) from bioethanol by-products, suggesting a high productivity from the same feedstock.

Surface modification of nanosatrch using nano silver: a potential antibacterial for food package coating.

Starch nanocrystal was prepared using weak sulfuric acid hydrolysis at 40°C. Transmission electron micrographs of dilute suspensions of starch nanocrystals showed round particles with a diameter ranging from 20 to 40nm. SEM of freeze dried samples showed separated particles between 40 and 100nm and confirmed production of starch nano particles. XRD patterns obtained for the prepared nanostarch and raw starch sample showed no special pattern of crystallinity for starch sample. Extracted nanostarch showed pattern of crystallinity with the peaks at Bragg angles (2θ) at about 15° and 23°, and a doublet at 17° and 18°. The crystalline structure of prepared sample was A-type. FTIR spectra confirmed the particles oxidation. Nano silver particle was precipitated on the starch nano particle. UV spectra confirmed the presence of silver particle on the starch particles. Inhibitions tests of nanostarch bearing nano silver on three types of bacteria was investigated. The inhibition test results were 25µg/mL for S. aureus, and S. typhi, and 12.5µg/mL for E. coli.

Optimization of cellulose nanocrystal length and surface charge density through phosphoric acid hydrolysis.

Cellulose nanocrystals (CNCs) are emerging nanomaterials with a large range of potential applications. CNCs are typically produced through acid hydrolysis with sulfuric acid; however, phosphoric acid has the advantage of generating CNCs with higher thermal stability. This paper presents a design of experiments approach to optimize the hydrolysis of CNCs from cotton with phosphoric acid. Hydrolysis time, temperature and acid concentration were varied across nine experiments and a linear least-squares regression analysis was applied to understand the effects of these parameters on CNC properties. In all but one case, rod-shaped nanoparticles with a high degree of crystallinity and thermal stability were produced. A statistical model was generated to predict CNC length, and trends in phosphate content and zeta potential were elucidated. The CNC length could be tuned over a relatively large range (238-475 nm) and the polydispersity could be narrowed most effectively by increasing the hydrolysis temperature and acid concentration. The CNC phosphate content was most affected by hydrolysis temperature and time; however, the charge density and colloidal stability were considered low compared with sulfuric acid hydrolysed CNCs. This study provides insight into weak acid hydrolysis and proposes 'design rules' for CNCs with improved size uniformity and charge density.This article is part of a discussion meeting issue 'New horizons for cellulose nanotechnology'.

Understanding Longitudinal Wood Fiber Ultra-structure for Producing Cellulose Nanofibrils Using Disk Milling with Diluted Acid Prehydrolysis.

Here we used dilute oxalic acid to pretreat a kraft bleached Eucalyptus pulp (BEP) fibers to facilitate mechanical fibrillation in producing cellulose nanofibrils using disk milling with substantial mechanical energy savings. We successfully applied a reaction kinetics based combined hydrolysis factor (CHFX) as a severity factor to quantitatively control xylan dissolution and BEP fibril deploymerization. More importantly, we were able to accurately predict the degree of polymerization (DP) of disk-milled fibrils using CHFX and milling time or milling energy consumption. Experimentally determined ratio of fibril DP and number mean fibril height (diameter d), DP/d, an aspect ratio measurer, were independent of the processing conditions. Therefore, we hypothesize that cellulose have a longitudinal hierarchical structure as in the lateral direction. Acid hydrolysis and milling did not substantially cut the “natural” chain length of cellulose fibrils. This cellulose longitudinal hierarchical model provides support for using weak acid hydrolysis in the production of cellulose nanofibrils with substantially reduced energy input without negatively affecting fibril mechanical strength.

Characterization of a Novel d-Glycero-d-talo-oct-2-ulosonic acid-substituted Lipid A Moiety in the Lipopolysaccharide Produced by the Acetic Acid Bacterium Acetobacter pasteurianus NBRC 3283

Acetobacter pasteurianus is an aerobic Gram-negative rod that is used in the fermentation process used to produce the traditional Japanese black rice vinegar kurozu. Previously, we found that a hydrophobic fraction derived from kurozu stimulates Toll-like receptors to produce cytokines. LPSs, particularly LPS from A. pasteurianus, are strong candidates for the immunostimulatory component of kurozu. The LPS of A. pasteurianus remains stable in acidic conditions during the 2 years of the abovementioned fermentation process. Thus, we hypothesized that its stability results from its structure. In this study, we isolated the LPS produced by A. pasteurianus NBRC 3283 bacterial cells and characterized the structure of its lipid A component. The lipid A moiety was obtained by standard weak acid hydrolysis of the LPS. However, the hydrolysis was incomplete because a certain proportion of the LPS contained acid-stable d-glycero-d-talo-oct-2-ulosonic acid (Ko) residues instead of the acid-labile 3-deoxy-d-manno-oct-2-ulosonic acid residues that are normally found in typical LPS. Even so, we obtained a Ko-substituted lipid A with a novel sugar backbone, α-Man(1–4)[α-Ko(2–6)]β-GlcN3N(1–6)α-GlcN(1–1)α-GlcA. Its reducing end GlcN(1-1)GlcA bond was also found to be quite acid-stable. Six fatty acids were attached to the backbone. Both the whole LPS and the lipid A moiety induced TNF-α production in murine cells via Toll-like receptor 4, although their activity was weaker than those of Escherichia coli LPS and lipid A. These results suggest that the structurally atypical A. pasteurianus lipid A found in this study remains stable and, hence, retains its immunostimulatory activity during acetic acid fermentation.

Using proteomics to characterise storage-induced aggregates in acidic whey protein isolate drinks

Formation of insoluble aggregates in acidic whey protein isolate (WPI) beverages during storage is a quality concern. Earlier studies showed that changes in processing methods from 95 °C for 180 s–120 °C for 20 s could prevent it. In the present study, WPI drinks were stored for up to 12 months and insoluble aggregates formed in re-solubilised WPI and its liquid phase analysed by proteomics. Insoluble aggregates were found to be enriched in caseinomacropeptides (CMP). Increased peptide formation by weak acid hydrolysis, especially of CMP, was found at 120 °C. Further enhanced hydrolysis of CMP was obtained by deamidation as well as by the presence of the genetic variant A of CMP. Batch variations may therefore be assigned to variations in CMP as well as variations in the distribution of genetic variants of A and B in different WPI batches used for the production of the WPI products.

Structural characterization of bioactive pectic polysaccharides from elderflowers (Sambuci flos)

Elderflowers have traditionally been used and are still used for its anti-inflammatory property. Traditionally elderflowers were used as remedies against cold, flu and diuretic. The aim of this study was to relate the structure of pectic-polysaccharides from elderflowers to immunomodulating properties. Purified fractions obtained by gelfiltration and ion exchange chromatography of 50% ethanol, 50°C water and 100°C water extracts exhibited strong complement fixating activity and macrophage stimulating activity. Reduced bioactivity was observed after removal of arabinose and 1,3,6-Gal linkages by weak acid hydrolysis. Enhanced bioactivity was observed after removal of estergroups by NaOH. Relating linkage analysis to the results of the bioactivity tests, led to the assumption that the branched moieties of the arabinogalactans linked to rhamnogalacturonan region, is important for the immunomodulating activity seen in elderflowers. No cytotoxity was observed.

Saccharification of agar using hydrothermal pretreatment and enzymes supplemented with agarolytic β-galactosidase

The major carbohydrate in red macroalgae is agarose, which is composed of d-galactose and 3,6-anhydro-l-galactose (AHG). So far, agarose saccharification was most efficiently achieved by prehydrolysis using a weak acid and subsequent enzymatic hydrolysis into monomeric sugars. However, this process requires rigorous neutralization after acid prehydrolysis, resulting in the formation of salts. Moreover, residual agarotriose is not further hydrolyzed by currently available β-agarases. In this study, we aimed at eliminating or minimizing the neutralization step by using a low-concentration acid-base buffer such as 20mM (0.3%, w/v) Tris–HCl for hydrothermal pretreatment of agar at 170°C for 10min. In order to hydrolyze agarotriose, an agarolytic β-galactosidase acting on odd-numbered agarooligosaccharides, was introduced into the enzymatic saccharification. Using these chemical and enzymatic processes, the monomeric sugar yields of 44.9% for galactose and 44.8% for AHG on the basis of their theoretical maximum amounts from the initial agar were obtained.

Structure–activity relationship of immunomodulating pectins from elderberries

The berries of Sambucus nigra have traditionally been used and are still used to treat respiratory illnesses such as cold and flu in Europe, Asia and America. The aim of this paper was to elucidate the structures and the immunomodulating properties of the pectic polymers from elderberries. All the purified fractions obtained from 50% ethanol, 50°C water and 100°C water extracts showed potent dose-dependent complement fixating activity and macrophage stimulating activity. The isolated fractions consisted of long homogalacturonan regions, in addition to arabinogalactan-I and arabinogalactan-II probably linked to a rhamnogalacturonan backbone. Reduced bioactivity was observed after reduction of Araf residues and 1→3,6 Gal by weak acid hydrolysis. The rhamnogalacturonan region in SnBe50-I-S3-I and SnBe50-I-S3-II showed higher activity compared to the native polymer, SnBe50-S3, after enzymatic treatment with endo-α-d-(1→4)-polygalacturonase. These results indicated that elderberries contained immunomodulating polysaccharides, where the ramified regions express the activities observed.

The Effect of Chemical and High‐Pressure Homogenization Treatment Conditions on the Morphology of Cellulose Nanoparticles

Cellulose nanoparticles were fabricated from microcrystalline cellulose (MCC) through combined acid hydrolysis with sulfuric and hydrochloric acids and high‐pressure homogenization. The effect of acid type, acid‐to‐MCC ratio, reaction time, and numbers of high‐pressure homogenization passes on morphology and thermal stability of the nanoparticles was studied. An aggressive acid hydrolysis was shown to lead to rod‐like cellulose nanocrystals with diameter about 10 nm and lengths in the range of 50–200 nm. Increased acid‐to‐MCC ratio and number of homogenization treatments reduced the dimension of the nanocrystals produced. Weak acid hydrolysis treatment led to a network of cellulose nanofiber bundles having diameters in the range of 20–100 nm and lengths of a few thousands of nanometers. The high‐pressure homogenization treatment helped separate the nanofiber bundles. The thermal degradation behaviors characterized by thermogravimetric analysis at nitrogen atmosphere indicated that the degradation of cellulose nanocrystals from sulfuric acid hydrolysis started at a lower temperature and had two remarkable pyrolysis processes. The thermal stability of cellulose nanofibers produced from hydrochloric acid hydrolysis improved significantly.

Weak Acid Hydrolysis of Proteins

Weak acid hydrolysis of proteins (WAHP) is a process where a weak acid solution is used at a high temperature to hydrolyze proteins. While high-temperature solutions of strong acids result in the complete hydrolysis of proteins into individual amino acids, WAHP predominantly cleaves aspartyl residues at the C-terminus and occasionally aspartic acid residues at the N-terminus but is ineffective at room temperature. Optimal cleavage is observed after 2 h at pH 2.0 and 108 °C. Recent investigations have shown that WAHP can be expedited by exposing the digestion mixture to microwave radiation. A previous article described microwave-assisted WAHP (MAWAHP) and confirmed the identities and relative abundances of hydrolyzed peptides using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) in positive ion reflectron mode. The present paper describes the use of a positive ion linear mode MALDI-MS in analyses of WAH hydrolysates of myoglobin. The experimental procedure was the same as that published previously except that the mass spectra were obtained in linear mode, which is more sensitive than reflectron mode. Figure 1 shows MALDI mass spectra of myoglobin after hydrolysis in 2% formic acid. Microwave-assisted digestion (Figure 1(a)) was performed for 1 h at three different temperatures (37 °C, 50 °C, and 100 °C). Digestion was also performed in boiling water without microwave irradiation (Figure 1(b)) at incubation times of 20, 40, 60, and 120 min. Protein peaks were observed in the mass spectra of myoglobin that had been hydrolyzed by MAWAH at 37 °C and 50 °C for 1 h and in the mass spectrum of myoglobin that had been hydrolyzed in boiling water for 20 min. Supplementary Figures S1 and S2 show enlarged mass spectra from m/z 1000 to m/z 8000 with complete assignments of the MAWAH hydrosylates of myoglobin and the

Microwave-assisted Weak Acid Hydrolysis of Proteins

Myoglobin was hydrolyzed by microwave-assisted weak acid hydrolysis with 2% formic acid at 37 o C, 50 o C, and 100 o C for 1 h. The most effective hydrolysis was observed at 100 o C. Hydrolysis products were investigated using matrix- assisted laser desorption/ionization time-of-flight mass spectrometry. Most cleavages predominantly occurred at the C-termini of aspartyl residues. For comparison, weak acid hydrolysis was also performed in boiling water for 20, 40, 60, and 120 min. A 60- min weak acid hydrolysis in boiling water yielded similar results as a 60-min microwave-assisted weak acid hydrolysis at 100 o C. These results strongly suggest that microwave irradiation has no notable enhancement effect on acid hydrolysis of pro- teins and that temperature is the major factor that determines the effectiveness of weak acid hydrolysis.