A new assay of chitosan in the presence of protein by hydrolysis with commercial α-amylase

A simple and rapid method for the assay of chitosan concentration was developed employing hydrolysis of chitosan by α-amylase. The hydrolyzed products were mainly glucosamine, N-acetylated glucosamine, and chitooligosaccharides and were determined colorimetrically using 3,5-dimethylsalicylic acid. The result observed that the absorbance at 540 nm was linear (regression coefficient: 0.9967) with respect to the concentration of chitosan. The content of chitosan determined by this method was comparable with that determined by either colorimetrical method or HPLC method. The new method is specific for estimation of chitosan, particularly in the sample containing protein with high accuracy, and can assay chitosan content up to 3.2 mg/mL.     

Antioxidant and tyrosinase inhibitory activities of a novel chitosan–phloroglucinol conjugate

A novel chitosan–phloroglucinol conjugate was developed by conjugating phloroglucinol onto a chitosan backbone. The chitosan–phloroglucinol conjugate was characterised by ¹H nuclear magnetic resonance (NMR), and the NMR spectra confirmed the conjugation. Antioxidant and tyrosinase inhibitory activities of the chitosan–phloroglucinol conjugate were investigated. The chitosan–phloroglucinol conjugate showed strong 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), hydrogen peroxide and ABTS⁺ radical scavenging activities as well as reducing power compared with those of the unmodified chitosan (P < 0.05). The formation of malondiadehyde (MDA) as an indicator of lipid peroxidation in a linoleic acid emulsion was 30.56 μM in the absence of the chitosan–phloroglucinol conjugate after 4 days incubation, whereas MDA was 4.14 μM in the presence of the chitosan–phloroglucinol conjugate (P < 0.05). The activity was higher than that of ascorbic acid, which is currently used as a food preservative. Moreover, the chitosan–phloroglucinol conjugate inhibited 56.30% tyrosinase activity, which is responsible for browning of foods, and acted as non‐competitive inhibitor. Taken together, the chitosan–phloroglucinol conjugate may have potential for application in functional foods and/or as a food preservative.     

Antibacterial Activities of Chitosans and Chitosan Oligomers with Different Molecular Weights on Spoilage Bacteria Isolated from Tofu

Seven bacteria were isolated from spoiled tofu and identified as Bacillus sp. (S08), B. megaterium (S10), B. cereus (S17, S27, S28, S32), and Enterobacter sakazakii (S35). In a paper disc test with 6 chitosans and 6 chitosan oligomers of different molecular weights, chitosans showed higher antimicrobial activity than did chitosan oligomers at a 0.1% concentration. Results of inhibitory effects of 6 chitosans on growth of Bacillus sp. (S08) failed to detect viable cells after incubation for 24 hrs at 37 C, even at 0.02% concentration. With B. megaterium (S10) and B. cereus (S27), a 3 to 4 log cycle reduction was found in the chitosan‐treated group. The growth of Enterobacter sakazakii (S35) was completely suppressed in the presence of 0.04% chitosan except for 1 chitosan product. The minimum inhibitory concentration of chitosan differed with products and isolates, ranging from 0.005% to above 0.1%.     

Effect of Molecular Weight,Acid, and Plasticizer on the Physicochemical and Antibacterial Properties of β‐Chitosan Based Films

Abstract: Effects of chitosan molecular weight (1815 and 366 kDa), type of acid (1% acetic, formic, and propionic acid, or 0.5% lactic acid) and plasticizer (0, 25% glycerol or sorbital w/w chitosan) on the mechanical, water barrier, and antibacterial properties of β‐chitosan films were investigated. Tensile strength (TS) of high molecular weight (Hw) films was 53% higher than that of low molecular weight (Lw) ones, acetate, and propionate films had the highest TS (43 and 40 MPa) among tested acids, and plasticizer‐reduced film TS 34%. Film elongation at break (EL) was higher in Hw films than in Lw ones, in which formate and acetate films were the highest (9% and 8%, respectively), and plasticizer increased the film EL 128%. Molecular weight of chitosan did not influence water vapor permeability (WVP) of the films. Acetate and propionate films had lower WVP than other acid types of films, and plasticizer increased film WVP about 35%. No difference was found between glycerol and sorbitol films in terms of film mechanical and water barrier properties. Lw β‐chitosan films showed significant antibacterial activity against E. coli and L. innocua. This study demonstrated that β‐chitosan films are compatible to α‐chitosan films in physicochemical properties and antibacterial activity, yet with simple sample preparation. Practical Application: β‐chitosan based edible films at molecular weight of about 300 kDa showed great antibacterial activity against Gram‐positive and Gram‐negative bacteria. The films have similar mechanical and water barrier properties to α‐chitosan based films at the similar molecular weight, but simple sample preparation procedures and more attractive color. The release of active chitosan fragment from the film matrix acts as an antibacterial agent, making β‐chitosan films suitable as intelligent food wraps or coatings for a wide range of food products to control moisture loss and prevent surface bacterial growth.     

Preparation of Acid‐Resistant Microcapsules with Shell‐Matrix Structure to Enhance Stability of Streptococcus Thermophilus IFFI 6038

Microencapsulation is an effective technology used to protect probiotics against harsh conditions. Extrusion is a commonly used microencapsulation method utilized to prepare probiotics microcapsules that is regarded as economical and simple to operate. This research aims to prepare acid‐resistant probiotic microcapsules with high viability after freeze‐drying and optimized storage stability. Streptococcus thermophilus IFFI 6038 (IFFI 6038) cells were mixed with trehalose and alginate to fabricate microcapsules using extrusion. These capsules were subsequently coated with chitosan to obtain chitosan‐trehalose‐alginate microcapsules with shell‐matrix structure. Chitosan‐alginate microcapsules (without trehalose) were also prepared using the same method. The characteristics of the microcapsules were observed by measuring the freeze‐dried viability, acid resistance, and long‐term storage stability of the cells. The viable count of IFFI 6038 in the chitosan‐trehalose‐alginate microcapsules was 8.34 ± 0.30 log CFU g^?1 after freeze‐drying (lyophilization), which was nearly 1 log units g^?1 greater than the chitosan‐alginate microcapsules. The viability of IFFI 6038 in the chitosan‐trehalose‐alginate microcapsules was 6.45 ± 0.09 log CFU g^?1 after 120 min of treatment in simulated gastric juices, while the chitosan‐alginate microcapsules only measured 4.82 ± 0.22 log CFU g^?1. The results of the long‐term storage stability assay indicated that the viability of IFFI 6038 in chitosan‐trehalose‐alginate microcapsules was higher than in chitosan‐alginate microcapsules after storage at 25 °C. Trehalose played an important role in the stability of IFFI 6038 during storage. The novel shell‐matrix chitosan‐trehalose‐alginate microcapsules showed optimal stability and acid resistance, demonstrating their potential as a delivery vehicle to transport probiotics.     

Modification of chitosan using hydrogen peroxide and ascorbic acid and its physicochemical properties including water solubility,oil entrapment and in vitro lipase activity

Chitosan was modified using H₂O₂ and ascorbic acid with different incubation temperatures (4–40 °C). The properties of modified chitosan, including its oil entrapment ability, water solubility and the lipase-resistant activities, using in vitro intestine model system were determined. Nuclear magnetic resonance analysis showed that ascorbic acid was bound to modified chitosan. All of the modified chitosan from 4 to 40 °C demonstrated improved water solubility (even in pH 7) compared to non-modified chitosan, which was only soluble at pH 4. Modified chitosan from 4 °C exhibited 27.40% of oil entrapment ability which was approximately four times higher than 6.87% of non-modified chitosan. Modified chitosan from 4 and 40 °C had increased resistance against lipase activity compared to other biopolymers, including beeswax, carnauba wax and non-modified chitosan. Modified chitosan could be used as a new food ingredient due to their high water solubility, oil-entrapping ability and resisting lipase activity.     

磁性壳聚糖改性对高岭土吸附蔗糖溶液中咖啡酸性能的影响

目的:研究磁性壳聚糖改性高岭土对模拟蔗汁中咖啡酸的吸附特性。方法:通过共沉淀法将壳聚糖、纳米四氧化三铁与高岭土结合制备成磁性壳聚糖改性高岭土,通过FT-IR、VSM和SEM表征高岭土改性前后表面结构和基团变化,采用吸附试验研究磁性壳聚糖改性高岭土对咖啡酸的吸附特性。结果:改性后壳聚糖和纳米Fe₃O₄成功地负载到了高岭土上并提升了其对咖啡酸的吸附性能,磁性壳聚糖改性高岭土的等电点为4.54,酸性条件有利于咖啡酸的去除,并在240 min时达到吸附平衡。磁性壳聚糖改性高岭土对咖啡酸的吸附过程更符合准二级动力学和Langmuir等温线吸附模型,其吸附过程主要为化学吸附和单分子层吸附,热力学研究表明吸附过程为自发吸热过程。结论:磁性壳聚糖改性高岭土对蔗汁中咖啡酸具有较强吸附性能,可作为糖用澄清剂用于蔗汁中咖啡酸的吸附处理。     

Control of Dongchimi Fermentation with Chitosan Deacetylated by Alkali Treatment to Prevent Over-Ripening

Abstract: Antimicrobial activities of chitosan against lactic acid bacteria were studied to apply for controlling dongchimi (whole-radish juicy kimchi) fermentation to prevent over-ripening. Antimicrobial activity of chitosan against lactic acid bacteria such as Leuconostoc mesenteroides and Lactobacillus plantarum was assayed at 10, 20, 30, and 40 mg/L concentration in the medium. The addition of 40 mg/L of the chitosan prepared at 140 °C for 10 min showed strong inhibitory effect on the growth of L. mesenteroides and L. plantarum. The effects of addition of chitosan to dongchimi have also been studied during fermentation at different temperatures of 4, 10, and 20 °C. Addition of chitosan decreased markedly viable cell counts of lactic acid bacteria such as Leuconostoc spp. and Lactobacillus spp. at the initial stage. Subsequently the lactic acid bacteria recovered the growth to the same level as non-chitosan treated dongchimi. During the dongchimi fermentation, the addition of chitosan at larger quantity up to 1000 mg/L (CS1000) prolonged the palatable fermentation period. Addition of chitosan in the dongchimi seemed to inhibit the growth of lactic acid bacteria, thereby lowering the acid content. It, therefore, caused the shelf life to be extended and resulted in a prolonged palatable period for the dongchimi.     

Effects of Immobilization and Permeabilization Procedures on Growth of Chenopodium rubrum Cells and Amaranthin Concentration

Cultures of Chenopodium rubrum were subjected to permeabilization and immobilization procedures to examine their potential for pigment production. Amaranthin content of culture media was highest for cultures treated with dimethylsulfoxide (DMSO) or dissolved chitosan. Labelling of the cells with L-(U-¹⁴C) tyrosine revealed that amaranthin was released from the cells but degraded rapidly. Product degradation in chitosan immobilized cells was delayed by 12–24 hr. Sufficient cell growth was observed in cultures treated with 0.77 mg chitosan per gram fresh biomass, with 0.42 ml.g^-1 DMSO, or when immobilized in a complex Ca-alginate-chitosan gel system. All other treatments resulted in inhibition of growth.     

Utilization of carboxymethyl chitosan in cosmetics

Carboxymethyl chitosan is a chitosan derivative of the most intensively investigated due to its water solubility in wider pH range compared with the parent compound, thus extended its use in various applications. In this review, different preparation conditions, which resulting in the N‐ and O‐carboxylated chitosan, diverse degree of substitution and water solubility are recapitulated. Five important features of carboxymethyl chitosan from recent studies, which are moisture absorption–retention, anti‐microbial properties, antioxidant capacities, delivery system and emulsion stabilization, have been centred and emphasized for cosmetic utilization. Additionally, cytotoxicity information has been inclusively incorporated to ensure its safety in application.     

Antibacterial action of chitosan

The antibacterial action of chitosan hydroglutamate (CH), chitosan lactate (CL) and chitosan derived from fungal mycelia was examined against both gram‐negative and gram‐positive bacteria. Plate counts indicated inactivation rates of one‐ to five‐log‐cycles within one hour. Fungal chitosan had significantly less antibiotic effect than CH and CL. The antibacterial action of CH and CL was very similar and shown to be concentration dependent with 0.1 mg/mL more effective than 2.0 and 5.0 mg/mL. When CH (or CL) and polygalacturonate were added to cell suspensions, death was prevented, possibly indicating that chitosan complexed with polygalacturonate could not penetrate the cell or disrupt the membrane. Leakage of intracellular components caused by chitosan was determined by exposing lactose‐induced Escherichia coli to chitosan with assay for ß‐galactosidase activity indicating that cell permeabilization occurred more extensively at the low chitosan concentrations. Microscopic examination showed that chitosan caused cell agglutination at pH 5.8. Injury to chitosan‐exposed Staphylococcus aureus MF‐31 could not be demonstrated using the criterion that sublethally stressed cells have increased sensitivity to high levels of sodium chloride.     

Enzymatic synthesis of chitosan–gelatin antimicrobial copolymer and its characterisation

BACKGROUND: Schiff bases can be formed by reaction between acylamino and the amino group with microbial transglutaminase (MTGase) as catalyst and used in protein crosslinking in the food industry. A novel chitosan–gelatin copolymer for coating meat products can be synthesised using MTGase as catalyst, with the characteristics of both chitosan and gelatin. The aim of the present study was to synthesise and characterise chitosan–gelatin antimicrobial copolymer. RESULTS: The yield of copolymer increased with increasing gelatin/chitosan ratio, while bacteriostasis of Staphylococcus aureus by the copolymer decreased, showing that its bacteriostatic ability depended on the amino group in chitosan. Under optimal synthesis conditions of 50 °C, pH 6 and 40 min reaction time the copolymer yield was 64.5% at a gelatin/chitosan ratio of 0.6. Bacteriostasis of S. aureus by 10 g kg⁻¹ copolymer solution was 70% of that by chitosan. CONCLUSION: A novel biological dressing frame material with excellent biocompatibility and antibacterial properties has been successfully prepared. The results of this study provide a background for further investigation of potential applications of chitosan–gelatin copolymer in the areas of agriculture and food. Copyright © 2009 Society of Chemical Industry     

Fe_3O_4/海藻酸盐微胶囊固定化细胞生长特性

采用脉冲电场液滴制备工艺,以海藻酸钠、壳聚糖为载体材料,纳米Fe3O4粉末为磁性材料,地衣芽孢杆菌为细胞模型,制备具有超顺磁性的微尺度载细胞微胶囊。以地衣芽孢杆菌的生长量为考察指标,考察不同磁含量、磁场引力、粒径和初始菌浓等因素的影响。实验结果表明,磁性材料Fe3O4的引入对地衣芽孢杆菌的生长没有影响。制备磁性固定化地衣芽孢杆菌微胶囊的最适条件为:Fe3O4含量0.003g/mL,初始接种密度为1.5倍菌浓(6.25×106个/mL),微囊的平均粒径为350μm,磁场环境的引入对地衣芽孢杆菌的生长无明显影响。论证了磁性壳聚糖/海藻酸钙微胶囊固定化细胞工艺进行在线分离,连续化操作的可行性。     

Effect of chitosan solution on the inhibition of Acidovorax citrulli causing bacterial fruit blotch of watermelon

BACKGROUND: The production of watermelon in China has been seriously hampered by fruit blotch disease and limited control measures are now applied. Chitosan has been employed to control a variety of plant diseases and is considered to be the most promising biochemical to control this disease. RESULTS: The in vitro antibacterial effect of chitosan and its ability in protection of watermelon seedlings from bacterial fruit blotch were evaluated. Results showed that three types of chitosan, in particular, chitosan A at 0.40 mg mL^?1 significantly inhibited the growth of Acidovorax citrulli. The antibacterial activity of chitosan A was affected by chitosan concentration and incubation time. The direct antibacterial activity of chitosan may be attributed to membrane lysis evidenced by transmission electron microscopic observation. The disease index of watermelon seedlings planted in soil and the death rate of seedlings planted in perlite were significantly reduced by chitosan A at 0.40 mg mL^?1 compared to the pathogen control. Fresh and dry weight of watermelon seedlings planted in soil was increased by chitosan seed treatment, but not by chitosan leaf spraying. CONCLUSION: The results indicated that chitosan solution may have a potential in controlling bacterial fruit blotch of watermelon. © 2013 Society of Chemical Industry     

Antibacterial Activity of Ozone‐Depolymerized Crawfish Chitosan

ABSTRACT: Antimicrobial activities of chitosan samples with different molecular weights (1333, 432, 201, 131, and 104 kDa) prepared by ozone treatment were examined against 2 Gram‐positive bacteria (Listeria monocytogenes and Staphylococcus aureus) and 2 Gram‐negative bacteria (Escherichia coli and Pseudomonas fluorescen) to investigate the effect of chitosan's molecular weight and concentration on the inhibition of bacterial growth. Antimicrobial activity of chitosan varied depending on the molecular weight, concentration of chitosan, and type of microorganism. Generally, the effectiveness of the chitosans significantly increased with increasing chitosan concentration, regardless of molecular size and types of bacteria. Chitosan with molecular weights ranging from 104 to 201 kDa showed relatively greater antimicrobial activity against L. monocytogenes, S. aureus, and P. fluorescen; whereas for E. coli, intermediate molecular weight chitosan was more effective in growth inhibition than lower or higher molecular weight chitosan particularly at 0.1% concentration.     

Antimicrobial activity of chitosan‐based films against Salmonella typhimurium and Staphylococcus aureus

The antibacterial effect of polyamide 6/66‐chitosan blend and chitosan‐coated plastic films was compared to chitosan films and chitosan solution, against Salmonella typhimurium and Staphylococcus aureus. The chitosan films did not show inhibition halos; however, contact inhibition was observed. During the tests, the films absorbed moisture, increasing of the diameter discs in relation to the concentration of the chitosan for both microorganisms at least 31%. Chitosan plastic film coating (bilayer system) showed only contact inhibition, without increase in contact area. The films from polyamide 6/66‐chitosan blend had no antibacterial activity. The highest inhibitory effect resulted from a chitosan solution at 1000 and 2000 ppm for S. typhimurium and S. aureus, respectively. The results of this study showed that the antimicrobial activity was lessened when the chitosan was combined with the plastic matrix because of the absence of contact inhibition, and the best activity was obtained with films prepared by casting of chitosan solution.     

Influence of molecular character of chitosan on the adsorption of chitosan to oil droplet interfaces in an in vitro digestion model

The relationship between the adsorption of chitosan to oil droplet interfaces (surface adsorption) and the molecular characteristics of the chitosan (molecular weight and charge density) was examined using an in vitro digestion model. This model involved adding different concentrations (3–10 wt%) of oil droplets to a 0.1 wt% chitosan solution at pH 3 to simulate consumption of an oil-containing meal after ingestion of chitosan. The pH was then incrementally raised to investigate pH variations that occur when a food material passes through the human digestive tract at an oil concentration of 3%. The amount of chitosan adsorbed to the oil droplet interface decreased with decreasing molecular weight (MW) and with increasing degree of deacetylation (DDA): ≈132, 85, and 78 g of oil per g of chitosan for MWs of 200, 500 and 750 kDa (all 90% DDA), respectively; and, 47, 65, and 78 g of oil per g of chitosan for DDAs of 40%, 70% and 90% (all 750 kDa), respectively at pH 3. In addition, the extent of droplet aggregation and the nature of the aggregates formed (strong versus weak; large versus small) also depended on chitosan characteristics. The pH dependence of the interaction between anionic oil droplets and cationic chitosan molecules depended on both MW and DDA. Microscope images showed formation of large flocculated structures at pH > 7 except for low DDA chitosan which remained soluble at all pH levels. Our results may have important consequences for understanding the bioactivity of chitosan, and for designing functional food ingredients to reduce lipid digestion and absorption.     

Microencapsulation of Bifidobacterium bifidum F‐35 in reinforced alginate microspheres prepared by emulsification/internal gelation

Alginate microspheres containing Bifidobacterium bifidum F‐35 prepared by emulsification/internal gelation were reinforced by blending with pectin or starch or coating with chitosan or poly‐L‐lysine to provide extra protection for the strain. The influence of these treatments on the size of microspheres, encapsulation yield (EY) and protective effect of microencapsulation on the cells was studied. No difference was detected in EY with different types of reinforcement, which was approximately 43–50%. The mean diameter of reinforced alginate microspheres ranged from 117 to 178 μm, reaching a maximum value when starch was incorporated in the alginate matrix. It was observed that the protective effects varied with the type of reinforcement. However, chitosan‐coated alginate microspheres provided the best protection for microencapsulated cells in simulated gastrointestinal tract and during 1 month of storage at 4 °C, and this system could be the comparatively effective vector of bifidobacteria for intestinal delivery.     

Effect of chitosan–Jicama starch coating on changes in qualities of fresh Nile tilapia (Oreochromis niloticus) fillets during ice storage

The effect of chitosan (0.5%)/Jicama starch (0%–4%)‐based edible coating on the quality of Nile tilapia (Oreochromis niloticus) fillets was evaluated over ice storage time. All samples were periodically analysed for pH value, thiobarbituric acid (TBA), total volatile basic nitrogen (TVB‐N), electrical conductivity (EC), total viable counts (TVC), total psychrotrophic counts (TPC), drip loss, colour, hardness and sensory characteristics. Results demonstrated that the quality of Nile tilapia fillets was preserved by the film containing chitosan and/or Jicama starch. Compared with chitosan coating alone (0.5% chitosan/0.25% glycerol) (P < 0.05), T3 (0.5% chitosan/1% Jicama starch/0.25% glycerol) had a better effect on the drip loss, TBA, TVC, TPC, hardness and sensory characteristics of the samples, thus indicating that low Jicama starch concentration (1%) enriched the coating ability of chitosan in extending the shelf life of Nile tilapia fillets.     

Characterization and antibacterial property of Kapok fibers treated with chitosan/AgCl–TiO2 colloid

The aim of this research is to investigate the antibacterial activity of Kapok fibers modified with AgCl/TiO₂ and Chitosan colloid. A very simple, single-step (pad-dry-cure) method was used for the application of AgCl/TiO₂ and Chitosan colloid on kapok fibers, the chemicals used are easily available. Different blend ratios of chitosan and AgCl/TiO₂ colloid were applied to the bleached kapok fibers and antibacterial properties were assayed against gram positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The treated kapok fibers were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). It was observed that the bacterial growth was significantly reduced in the samples which had a higher concentration of chitosan and AgCl/TiO₂ colloid. However, a significant reduction in bacterial growth with the use of this colloid was observed.