细菌纤维素在生物医学材料中应用的研究进展

细菌纤维素是一种天然的生物高聚物,具有生物活性、生物可降解性、生物适应性,具有独特的物理、化学和机械性能,例如高的结晶度、高的持水性、超细纳米纤维网络、高抗张强度和弹性模量等,因而成为近来国际上新型生物医学材料的研究热点。本文概括了细菌纤维素的性质、研究历史以及在生物医学材料上的应用,重点阐述了细菌纤维素在组织工程支架、人工血管、人工皮肤和治疗皮肤损伤方面的应用以及当前研究现状。     

Application of bacterial cellulose pellets in enzyme immobilization

Over recent years, there has been a growing interest in the use of cellulose materials in bioprocessing technologies. Bacterial cellulose which is the pure cellulose has unique physical properties which differ from those of plant cellulose and has therefore attracted attention as a new functional material. The applications of bacterial cellulose rarely use the pellet type but it has potential in enzyme immobilization since pellet form is usually used in this field. In this research, Glucoamylase which is widely used in the food industry was immobilized on bacterial cellulose beads after testing using various activation procedures. The results showed that the epoxy method with glutaraldehyde coupling was the best method. After comparison of the different types of bacterial cellulose beads for glucoamylase immobilization, the wet bacterial cellulose beads of the smallest size (0.5–1.5 mm) were the best support. The immobilization of enzyme enhances its stability against changes in the pH value and temperature especially in the lower temperature region. The relative activity of the immobilized glucoamylase was still above 77% at pH 2.0 and it was the highest value in the literature. The relative activities were more than 68% in the lower temperature region even at 20 °C. Thus, bacterial cellulose beads are a practical potential support for the preparation of immobilized enzymes in industrial applications.     

In situ synthesis of CdS nanoparticles on bacterial cellulose nanofibers

CdS nanoparticles have been synthesized and stabilized on unique bacterial cellulose (BC) nanofibers in situ. The obtained nanocomposite material have been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), fourier transformed infrared (FTIR), thermogravimetric analysis (TGA), ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopy. The results indicated that CdS nanoparticles of about 30 nm diameter deposited on BC nanofibres are well-dispersed in the BC nanofibre-network and the uniform spherical CdS nanoparticles are comprised of nano-sized CdS crystal. Moreover, the crystallite sizes of CdS crystals are about 8 nm. The nanocomposites would have potential application as photocatalyst, novel luminescence and photoelectron transfer devices.     

Utilization of residues from agro-forest industries in the production of high value bacterial cellulose

Bacterial cellulose (BC), a very peculiar form of cellulose, is gaining considerable importance due to its unique properties. In this study, several residues, from agro-forestry industries, namely grape skins aqueous extract, cheese whey, crude glycerol and sulfite pulping liquor were evaluated as economic carbon and nutrient sources for the production of BC. The most relevant BC amounts attained with the residues from the wine and pulp industries were 0.6 and 0.3 g/L, respectively, followed by biodiesel crude residue and cheese whey with productions of about, 0.1 g/L after 96 h of incubation. Preliminary results on the addition of other nutrient sources (yeast extract, nitrogen and phosphate) to the residues-based culture media indicated that, in general, these BC productions could be increased by ∼200% and ∼100% for the crude glycerol and grape skins, respectively, after the addition organic or inorganic nitrogen.     

Use of a bacterial cellulose filter for the removal of oil from wastewater

The present study describes the development of a bacterial cellulose (BC) filter for the treatment of oily waters. BC membranes were produced using an alternative medium containing 2.5 % corn steep liquor. Samples of previously purified membranes were characterized and tested as filters for the separation of oil from water (oil concentrations of 10, 150 and 230 ppm). Flow rate, filter diameter and membrane thickness after 6 and 10 days of cultivation were evaluated in a filtration system constructed in polyvinyl chloride. The BC membranes presented satisfactory flexibility, thermal stability and mechanical strength. However, the membrane obtained after 10 days supported 100 % more force than the membrane obtained after 6 days. The experiments revealed 100 % removal of the oil from all emulsions. The filtration flow rate increased proportionally to the filter diameter and decreased from the 6-day membrane to the 10-day membrane. The results of the present study are promising and demonstrate the efficiency, durability and strength of this novel biodegradable, non-toxic material for the treatment of oily waters generated during industrial activities.     

Gluconacetobacter sp. gel_SEA623-2, bacterial cellulose producing bacterium isolated from citrus fruit juice

Cellulose producing bacterial strain was isolated from citrus fruit juice fungus. The isolated strain was identified as Gluconacetobacter sp. gel_SEA623-2 based on several morphological characteristics, biochemical tests, and 16S rRNA conducted. Culture conditions for bacterial cellulose production by SEA623-2 were screened in static trays. Conditions were extensively optimized by varying the kind of fruit juice, pH, sugar concentration, and temperature for maximum cellulose production. SEA623-2 has a high productive capacity in citrus processing medium, but not in other fruits. The optimal combination of the media constituents for bacterial cellulose production is as follows: 10% citrus juice, 10% sucrose, 1% acetic acid, and 1% ethanol at 30 °C, pH 3.5. Bacterial cellulose produced by SEA623-2 has soft physical properties, high tensile strength, and high water retention value. The cellulose produced by the selected bacteria is suitable as a cosmetic and medical material.     

Homogenous reactions of cellulose from different natural sources

Two different homogenous reactions on bacterial cellulose (BC), kenaf fiber (KF) and microcrystalline cellulose (MC) were performed to monitor their chemical reactivity. The first reaction was selective oxidation of the primary hydroxyl group with sodium chlorite in the presence of catalytic amount of sodium chloride. While, the second was the formation of triester hypoiodous cellulose using potassium iodate and potassium iodide. The chemical structures of these derivatives were investigated using FT-IR and solid state ¹³C NMR spectroscopies. The BC fibrils required the shortest time among these cellulose samples for both reactions, whereas the viscosity values of BC after iodination and oxidation have the best values compared to KF and MC. FT-IR results show the absence of the hydroxy group of BC and a weak absorption band in both KF and MC. On the other hand, the crystallinity index (CI) of BC is higher than those of both KF and MC. FT-IR spectra of the oxidized different cellulose samples, confirmed the presence of a strong absorption band at around 1590 cm⁻¹ that attributed to vibration band of carbonyl group of carboxylic moiety. Moreover, in the ¹³C NMR spectrum of oxidized cellulose, the lack of signal at 62 ppm and the appearance of signal at 171 ppm indicated that the primary alcohol group is completely oxidized to carboxylic acid. These results showed that BC had a higher reactivity than other samples due to its great purity and low degree of polymerization.     

Production of bacterial cellulose from Komagataeibacter saccharivorans strain BC1 isolated from rotten green grapes

Abstract

Bacterial cellulose (BC) is one of the prominent biopolymers that has been acquiring attention currently due to its distinctive properties and applications in various fields. The current work presents the isolation of Komagataeibacter saccharivorans strain BC1 isolated from rotten green grapes, followed by biochemical and genotypic characterization, which confirmed that the strain is capable of synthesizing cellulose. Further, production media was designed and certain variables such as carbon, nitrogen sources, pH, and temperature were optimized in order to obtain the maximum concentration of cellulose production. We found mannitol to be the ideal carbon source and yeast extract as the ideal nitrogen source with a highest BC dry yield of 1.81?±?0.25?g/100?mL at pH 5.76 for a week at 30?°C.The charcterization of pellicles by FTIR spectrum depicted similar functional groups present in synthesized BC as that of the commercial cellulose. X-ray diffraction revealed that BC showed 82% crystallinity. Surface morphology of the dried pellicle was studied by SEM image which showed that the BC surface was tightly packed with thin fibers with less porosity. Hence the study demonstrates that the isolates of K.saccharivorans could be used to produce a biopolymer in a short period of time using a modified production medium.     

细菌纤维素性质及应用的研究进展

细菌纤维素是由微生物合成的多孔性网状纳米级生物高分子材料,由于它具备高持水性、高透气性、良好生物相容性、高机械强度、三维网络结构等独特性质,因此在纺织、医用敷料、组织工程、食品、导电材料等行业具有广阔的应用前景。本文主要从性质和应用两方面对其近年来的研究进展做了综述,并对未来的发展做了展望。     

Ultrasound‐assisted swelling of bacterial cellulose

Bacterial cellulose (BC) was obtained by static cultivation using commercial BC gel from scoby. BC membranes (oven dried and freeze‐dried) were swelled with 8% NaOH, in the absence and in the presence of ultrasound (US), for 30, 60, and 90 min. The influence of swelling conditions on both physico‐chemical properties and molecules entrapment was evaluated. Considering the highest levels of entrapment, an optimum swelling procedure was established: 8% NaOH for 30 min at room temperature in the presence of US. Native and PEGylated laccase from Myceliophthora thermophila was immobilized on BC membranes and a different catalytic behaviour was observed after immobilization. Native laccase presented activity values similar to published reports (5–7 U/gBC) after immobilization whereas PEGylated enzymes showed much lower activity (1–2 U/gBC). BC swelled membranes are presented herein as a potential support for the preparation of immobilized enzymes for industrial applications, like phenolics polymerization.     

Poly(3-hydroxubutyrate-co-4-hydroxubutyrate)/bacterial cellulose composite porous scaffold: Preparation, characterization and biocompatibility evaluation

Bio-composite scaffolds were prepared by freeze-drying using poly(3-hydroxubutyrate-co-4-hydroxubutyrate) (P(3HB-co-4HB)) and bacterial cellulose (BC) as raw materials and trifluoroacetic acid (TFA) as co-solvent. The characteristics of the composite scaffold were investigated by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), water contact angle measurement and tensile testing. Preliminary biodegradation test was performed for P(3HB-co-4HB) and P(3HB-co-4HB)/BC composite scaffold in buffer solution and enzyme solution. The biocompatibility of the composite scaffold was preliminarily evaluated by cell adhesion studies using Chinese Hamster Lung (CHL) fibroblast cells. The cells incubated with composite scaffold for 48 h were capable of forming cell adhesion and proliferation, which showed better biocompatibility than pure P(3HB-co-4HB) scaffold. Thus, the prepared P(3HB-co-4HB)/BC composite scaffold was bioactive and may be suitable for cell adhesion/attachment suggesting that these scaffolds can be used for wound dressing or tissue-engineering scaffolds.     

Increased water content in bacterial cellulose synthesized under rotating magnetic fields

The current study describes properties of bacterial cellulose (BC) obtained from Komagataeibacter xylinus cultures exposed to the rotating magnetic field (RMF) of 50 Hz frequency and magnetic induction of 34 mT for controlled time during 6 days of cultivation. The experiments were carried out in the customized RMF exposure system adapted for biological studies. The obtained BC displayed an altered micro-structure, degree of porosity, and water-related parameters in comparison to the non-treated, control BC samples. The observed effects were correlated to the duration and the time of magnetic exposure during K. xylinus cultivation. The most preferred properties in terms of water-related properties were found for BC obtained in the setting, where RMF generator was switched off for the first 72 h of cultivation and switched on for the next 72 h. The described method of BC synthesis may be of special interest for the production of absorbent, antimicrobial-soaked dressings and carrier supports for the immobilization of microorganisms and proteins.     

A mechanically strong, flexible and conductive film based on bacterial cellulose/graphene nanocomposite

A highly flexible nanocomposite film of bacterial cellulose (BC) and graphene oxide (GO) with a layered structure was presented using the vacuum-assisted self-assembly technique. Microscopic and X-ray diffraction measurements demonstrated that the GO nanosheets were uniformly dispersed in the BC matrix. The interactions between BC and GO were studied by Fourier transformation infrared spectroscopy. Compared with pristine BC, the integration of 5 wt% GO resulted in 10% and 20% increase in Young's modulus and tensile strength of the composite film. The electrical conductivity of the composite film containing 1 wt% GO after in situ reduction showed a remarkable increase by 6 orders of magnitude compared with the insulated BC.     

A novel thermotropic liquid crystalline – Benzoylated bacterial cellulose

Using the esterification of bacterial cellulose (BC), we have synthesized Benzoylated bacterial cellulose (BBC). The molecular structure of the BBC was characterized by means of Fourier transform infrared (FT-IR) spectroscopy, ¹H and ¹³C nuclear magnetic resonance (NMR). The BBC is found to display thermotropic liquid crystalline feature determined with differential scanning calorimetry (DSC), polarized optical microscope (POM) and wide-angle X-ray diffraction (WAXD). Here, we demonstrate that it is possible to obtain the BBC with degree of substitution (DS) from 0.88 to 2.46 by applying the different molar ratio of benzoyl chloride to the anhydrous glucose unit (AGU). The glass transition temperatures (T_g) of the liquid crystalline phases lie between 281.2 and 281.8 °C and the isotropic melt transition temperatures (T_i) vary from 341.6 to 362.8 °C, depending on the DS.     

The three-dimensional morphology of aggregates of native cotton cellulose microfibrils

The three-dimensional morphology of native bacterial cellulose is confirmed by scanning electron microscopy. In addition, it is shown by scanning electron microscopy, and transmission electron microscopy with positive staining by phosphotungstic acid ions that aggregates of microfibrils of native cotton cellulose have a similar structure. The results are consistent with previous reports on microfibrils of algal cellulose. These observations exclude a simple spinneret process as a mechanism of formation of the microfibrils of these sources of cellulose.     

Preparation of chitin/cellulose composite gels and films with ionic liquids

In this study, we performed preparation and characterizations of the chitin/cellulose composite gels and films using the two ionic liquids, 1-allyl-3-methylimidazolium bromide and 1-butyl-3-methylimidazolium chloride. First, chitin and cellulose were dissolved in each appropriate ionic liquid. Then, the two liquids were mixed in the desired ratios at 100 °C to give the homogeneous mixtures. The gels were obtained by standing the mixtures for 4 days. On the other hand, the films were obtained by casting the mixtures on glass plates, followed by soaking in water and drying. The obtained gels and films were characterized by XRD and TGA measurements. The mechanical properties of the gels and films were evaluated under compressive and tensile modes, respectively.     

Statistical optimization of bacterial cellulose production by Leifsonia soli and its physico-chemical characterization

Bacterial cellulose has multiple applications in various industries such as food, biomedical, textile due to its uniqueness of being a better bio-compatible coating agent, binding material, etc. In this study, optimization of the culture medium for producing BC from Leifsonia soli was carried out by selecting different parameters. Five significant factors such as maltose, pH, incubation days, soy whey and calcium chloride were estimated through ANOVA based response surface methodology. Maximum cellulose production (5.97 g/L) was obtained where maltose 1 % (w/v) supplemented with 0.8 % (v/v) soy whey and calcium chloride 0.8 % (w/v) at pH 6.5 for 7 days of incubation. In addition, assurance of cellulose production from bacteria was done by using High-performance liquid chromatography analysis. Further, the structure and purity of obtained cellulose were examined by SEM and elemental analysis where it was observed that the sample holds the value of carbon 44.1 ± 0.20 % and hydrogen 6.2 ± 0.3 %, respectively. This study concludes that the addition of maltose and soy whey could be used as carbon, nitrogen sources and calcium chloride was used as an additive for the bacterial cellulose production compared to the Hestrin Schramm medium. In addition, the calculated water holding capacity of the sample was found to be 73 %.     

细菌纤维素的研究进展

细菌纤维素是由醋酸杆菌属、根瘤菌属、土壤杆菌属、八叠球菌属等的某些细菌在一定条件下产生的,其中最有代表性的细菌是木醋杆菌。与传统植物纤维素相比,细菌纤维素具有很高的化学纯度。主要介绍细菌纤维素性质、生物合成的方法及其在食品工业、造纸工业和作为一种生物材料在医学工程等方面的应用。