Chemo-enzymatic Synthesis of Novel Oligo-N-acetyllactosamine Derivatives having a β(1-4)–β(1-6) Repeating Unit by Using Transition State Analogue Substrate

Chitinase-catalyzed hydrolytic and transglycosylating behavior of 1,2-oxazoline derivative of N-acetyllactosamine (LacNAc-oxa) 1 has been investigated. An extremely rapid hydrolysis (ring-opening of the oxazoline moiety) could be observed, suggesting that 1 behaves as a transition state analogue substrate for chitinase A1 (Bacillus circulans WL-12). This disaccharide monomer 1 was found to polymerize under basic conditions, giving rise to novel oligosaccharides having a β(1-4)–β(1-6) repeating unit in the main chain. The degree of polymerization of the resulting oligosaccharides was up to 5. This is the first example of enzymatic glycosylation reaction forming a β(1-6) bond catalyzed by chitinase.     

Synthesis and Properties of Surfactants derived from N‐Acetyl‐D‐Glucosamine

The synthesis of 2‐acetamido‐2‐deoxy‐6‐O‐octanoyl‐D‐glucono‐1,5‐lactone 9 and 2‐acetamido‐2‐deoxy‐6‐O‐octanoyl‐α‐D‐glucopyranose 7 from 2‐acetamido‐2‐deoxy‐α‐D‐glucopyranose is reported. For both targets, the key intermediate was allyl 2‐acetamido‐3,4‐di‐O‐benzyl‐2‐deoxy‐6‐O‐octanoyl‐α‐D‐glucopyranoside 5. Surface tension measurements (critical micellar concentration of 22.3 mM and 5 mM for 9 and 7, respectively) showed up the surface activity of both compounds, while enzyme inhibition assays indicated that 9 could inhibit bovine β‐N‐acetylglucosaminidase (K_i=6.5 µM) but not Serratia marcescens chitobiase nor hen egg‐white lysozyme. Moreover, 7 was shown to induce chitinase production of S. marcescens and to be readily metabolized by these bacteria.      

Inhibitory analysis of the effect of polycyclic aromatic hydrocarbons on the activity of chitinase by means of liquid chromatography-mass spectrometry of chitin oligosaccharides

The analytical method of determining enzyme activity by liquid chromatography-mass spectrometry (LC/MS) was developed and applied for investigation of the effect of polycyclic aromatic hydrocarbons (PAHs) on the enzyme activity of chitinase. The measurement of chitinase activity by LC/MS is useful in order to use the nonderivatized substrate, which can show in vivo chitinase activity. Substrate consumption and product formation were monitored in order to determine chitinase activity. It was shown that, for the first time, in vitro addition of PAHs inhibited the activity of chitinase in a noncompetitive manner. The IC₅₀ value of benzo[a]pyrene was 1.4 μM, and PAHs containing four or more aromatic rings showed the same or higher inhibitory effect, whereas PAHs with a lower number of aromatic rings showed lower inhibition of the chitinase activity than benzo[a]pyrene.     

Purification and Characterization of Thermostable Chitinase from <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> SK-1

Chitinase was purified from the culture medium of Bacillus licheniformis SK-1 by colloidal chitin affinity adsorption followed by diethylamino ethanol-cellulose column chromatography. The purified enzyme showed a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The molecular size and pI of chitinase 72 (Chi72) were 72 kDa and 4.62 (Chi72) kDa, respectively. The purified chitinase revealed two activity optima at pH 6 and 8 when colloidal chitin was used as substrate. The enzyme exhibited activity in broad temperature range, from 40 to 70°C, with optimum at 55°C. It was stable for 2 h at temperatures below 60°C and stable over a broad pH range of 4.0–9.0 for 24 h. The apparent K _m and V _max of Chi72 for colloidal chitin were 0.23 mg ml⁻¹ and 7.03 U/mg, respectively. The chitinase activity was high on colloidal chitin, regenerated chitin, partially N-acetylated chitin, and chitosan. N-bromosuccinamide completely inhibited the enzyme activity. This enzyme should be a good candidate for applications in the recycling of chitin waste.     

Early diagnosis of blast fungus, Magnaporthe oryzae, in rice plant by using an ultra-sensitive electrically magnetic-controllable electrochemical biosensor

As one of the most destructive and widespread disease of rice, Magnaporthe oryzae (also called Magnaporthe grisea) has a significant negative impact on rice production. Therefore, it is still in high demand to develop extremely sensitive and accurate methods for the early diagnosis of Magnaporthe oryzae (M. oryzae). In this study, we developed a novel magnetic-controllable electrochemical biosensor for the ultra sensitive and specific detection of M. oryzae in rice plant by using M. oryzae’s chitinases (Mgchi) as biochemical marker and a rice (Oryza sativa) cDNA encoding mannose-binding jacalin-related lectin (Osmbl) as recognition probe. The proposed biosensor combined with the merits of chronoamperometry, electrically magnetic-controllable gold electrode and magnetic beads (MBs)-based palladium nano-particles (PdNPs) catalysis amplification, has an ultra-high sensitivity and specificity for the detection of trace M. oryzae in rice plant. It could be used to detect M. oryzae in rice plant in the initial infection stage (before any symptomatic lesions were observed) to help farmers timely manage the disease. In comparison with previous methods, the proposed method has notable advantages such as higher sensitivity, excellent specificity, short analysis time, robust resistibility to complex matrix and low cost etc. The success in this study provides a reliable approach for the early diagnosis and fast screening of M. oryzae in rice plant.     

Enzyme assay for chitinase catalyzed hydrolysis of tetra-N-acetylchitotetraose by isothermal titration calorimetry

Isothermal titration calorimetry (ITC) has been used to observe the chitinase-catalyzed hydrolysis of tetra-N-acetylchitotetraose. Enzymatic hydrolysis of tetra-N-acetylchitotetraose by chitinase B from Serratia marcescens produces exclusively two molecules of di-N-acetylchitobiose allowing for the determination of a single glycosidic bond hydrolysis heat that was used to monitor the rate of the enzymatic reaction. The change in heat rate with respect to time (dQ/dt) was translated to the reaction rate, and the total heat produced was related to substrate concentration throughout the reaction. Reaction rates versus substrates concentration were fit to Michaelis-Menten plots, yielding a k_cat of 40.9 ± 0.5 s⁻¹ and a K_m of 54 ± 2 μM.     

Effect of Agitation and Aeration Rates on Chitinase Production Using Trichoderma virens UKM1 in 2-l Stirred Tank Reactor

Shrimps have been a popular raw material for the burgeoning marine and food industry contributing to increasing marine waste. Shrimp waste, which is rich in organic compounds is an abundant source of chitin, a natural polymer of N-acetyl-D-glucosamine (GluNac), a reducing sugar. For this respect, chitinase-producing fungi have been extensively studied as biocontrol agents. Locally isolated Trichoderma virens UKM1 was used in this study. The effect of agitation and aeration rates using colloidal chitin as control substrate in a 2-l stirred tank reactor gave the best agitation and aeration rates at 200 rpm and 0.33 vvm with 4.1 U/l per hour and 5.97 U/l per hour of maximum volumetric chitinase activity obtained, respectively. Microscopic observations showed shear sensitivity at higher agitation rate of the above system. The oxygen uptake rate during the highest chitinase productivity obtained using sun-dried ground shrimp waste of 1.74 mg of dissolved oxygen per gram of fungal biomass per hour at the kappaL a of 8.34 per hour.     

Overexpression of an Endochitinase Gene (<Emphasis Type="Italic">ThEn-42</Emphasis>) in <Emphasis Type="Italic">Trichoderma atroviride</Emphasis> for Increased Production of Antifungal Enzymes and Enhanced Antagonist Action Against Pathogenic Fungi

Trichoderma is one of the most promising biocontrol agents against plant fungal diseases. In this study, a transgenic strain of Trichoderma atroviride was characterized. The transgenic strain contains an endochitinase gene (ThEn-42) driven by the cellulase promoter cbh1 of T. reesei for overexpression of ThEn-42. The culture filtrates of the transformant and the parental strain grown in eight different media were evaluated for chitinase and antifungal enzyme production based on activity gels, protein profiles, and antifungal activities. Results demonstrated that chitinases are important components and synergistic interactions play a key role in the antagonistic action of T. atroviride. Moreover, altering medium nutrient concentration and composition led to enhanced production of antifungal enzymes, a potential strategy for mass production. Two of the culture filtrates contained almost pure endochitinase, and could be excellent commercial sources for this enzyme. Several culture filtrates were highly antifungal. Two filtrates were so effective in biocontrol of a fungal pathogen, Penicillium digitatum, that they not only inhibited spore germination but destroyed the spores completely when 20 μl of culture filtrate (corresponding to approximately 104 μg of total protein) was applied in a total volume of 150 μl (approximately 0.7 mg protein ml⁻¹).     

Detection of Chitinolytic Enzymes in Ipomoea Batatas Leaf Extract by Activity Staining after Gel Electrophoresis

A non‐denatured SDS‐PAGE followed by in‐gel activity staining using embedded glycol chitin as a substrate was used to identify the proteins with chitinolyitc activities from sweet potato leaf extract. At least two chitinase activity zones can be clearly identified on the gel at positions with estimated molecular weights of 54.1～55.6 kDa and 39.6 kDa. Furthermore, our data also indicate that the activity of the larger one can withstand the standard SDS‐PAGE sample preparation. Both of these chitinases, however, are different from that of the previously identified chitinase in sweet potato leaves, which has a molecular weight of 16 kDa. By using an embedded substrate, our method has superior sensitivity in detecting chitinases with higher molecular weights. It is a simple, affordable way and may aid in the future discovery of new chitinases.     

Enhancing Stability and Purity of Crude Chitinase of Achatina fulica by Crystallization

A crystallization method was developed to enhance the purity and stability of hydrolase mixtures from the digestive gland of the snail Achatina fulica, as demonstrated by chitinase activity. Crude chitinase was concentrated by freeze drying and then crystallized at 10 °C. Crystal formation was observed under the microscope. The best concentration for crystallization was obtained with 1.5-fold concentrated crude chitinase. Crystallization enhanced the chitinase specific activity from 0.87 U mg^-1 to 0.95 U mg^-1. The loss of chitinase activity from liquid and crystals of crude chitinase on four days storage at 10 °C was 83.0% and 17.7%, respectively. It was concluded that the crude chitinase crystals showed a significant increase in stability and purity.