Microbial exopolysaccharides (EPS) are an abundant and important group of compounds that can be secreted by bacteria, fungi and algae. The biotechnological production of these substances represents a ...faster alternative when compared to chemical and plant-derived production with the possibility of using industrial wastes as substrates, a feasible strategy after a comprehensive study of factors that may affect the synthesis by the chosen microorganism and desirable final product. Another possible difficulty could be the extraction and purification methods, a crucial part of the production of microbial polysaccharides, since different methods should be adopted. In this sense, this review aims to present the biotechnological production of microbial exopolysaccharides, exploring the production steps, optimization processes and current applications of these relevant bioproducts.
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•The potential use of banana peel to produce cellulose nanofibers was investigated.•A process conditions study to obtain nanofibers by enzymatic hydrolysis was conducted using a 24-1 ...fractional factorial design.•Alkaline treatment was a necessary step to remove the amorphous fraction present in the fiber.•Optimization of the enzymatic hydrolysis process conditions enabled production of typical cellulose nanofibers.•Banana peel nanoparticles have potential application as reinforcing elements in composites.
Cellulose nanofibers (CNFs) were isolated from banana peel bran via alkaline treatment followed by enzymatic treatment with xylanase. The influence of process conditions such as pH, temperature, and concentrations of the enzyme and substrate on the properties of the CNFs was evaluated with a 24−1 fractional factorial design with three central points. Enzyme at 70U/g of bran, substrate at 15%, pH 6.0, and temperature between 35 and 55°C favored enzymatic hydrolysis. Transmission electron microscopy (TEM) images confirmed that treatment with xylanase effectively isolated cellulose fibers at the nanometer scale. Fourier transform infrared spectroscopy (FTIR) showed that a fraction of amorphous compounds was removed. X-ray diffraction revealed that the CNFs presented high crystallinity index (66.2%). The CNFs had a diameter of 3.7nm, their aspect ratio was in the range of long nanofibers, and their suspension was stable (−29.1mV). These features make the CNFs potentially applicable as reinforcing agents in composites. The results evidenced that enzymatic hydrolysis with xylanase successfully afforded CNFs from banana peel, a residue that constitutes a potential source of biodegradable materials of commercial interest.
The physicochemical and antimicrobial properties of starch−chitosan films incorporated with oregano essential oil (OEO) have been investigated. The antimicrobial effects of starch−chitosan−OEO films ...against Bacillus cereus, Escherichia coli, Salmonella enteritidis, and Staphylococcus aureus were determined by the disk inhibition zone method. The film mechanical properties, water vapor permeability (WVP), Fourier transform infrared spectra (FTIR), and thermograms (TGA) were also determined. Films added with OEO effectively inhibited the four microorganisms tested and demonstrated improved barrier properties. The presence of OEO in starch−chitosan films led to the formation of more flexible films. Chitosan was not effective against the tested organisms, but it decreased film rigidity and WVP. TGA analysis demonstrated that the addition of chitosan and OEO did not affect the thermal stability of the films.
New edible coatings made of cassava starch and babassu flour were applied on cagaita and mangaba, two typical fruits from the Brazilian Cerrado, by dipping method. The effect of the babassu flour ...concentration (10, 30, or 50 g/100 g of starch) on the properties of coated fruits were studied. Fruits treated with cassava starch coating added with 50% babassu flour provided the most satisfactory results in terms of weight loss: mass loss was only 14% and 7% for cagaitas and mangabas, respectively. Meanwhile, uncoated fruits experienced greater weight loss up to 35%, indicating water loss due to product degradation during storage period and led to weight loss. Therefore, edible coatings protected fruits from dehydration. Uncoated fruits had the highest increase in a* parameter, which provided them with a more reddish color and faster ripening rate. Total soluble solids were stable for coated fruits along storage. All treatments showed an increase in pH values attributed to the degradation of organic acids in fruits. These results are in agreement with the acidity reduction reported for mangabas. Unlike mangabas, acid values increased in cagaitas which was associated with galacturonic acid formation by pectinesterase. Overall, cassava starch added with babassu flour is a promising material to produce edible coatings with adequate physical properties for food applications.
Summary
Despite the increased use of extrusion technology in the production of biodegradable films, a better understanding of its effects on the several biopolymers is required. Therefore, the ...influence of extrusion temperature (120, 130 and 140 °C) and screw speed (25, 35 and 45 r.p.m.) on the properties of an active film formulated with starch, chitosan and oregano essential oil was investigated. Mechanical and barrier properties, apparent opacity and blow‐up ratio (BUR) of films were determined. The increase in screw speed had a positive effect on BUR and water vapour permeability (WVP) and a negative effect on opacity, tensile strength and elongation at break of the films. Low die temperatures resulted in decreased tensile strength, elongation at break, Young’s modulus and WVP of the films. Sorption isotherms of films were directly influenced by the extrusion conditions and films produced at 130 °C and 35 r.p.m. were less hydrophilic.
► Starch–chitosan–glycerol blends were studied in extruded films. ► Small amounts of chitosan (<5%) increase the mechanical resistance of starch films. ► Intermolecular hydrogen bonds between ...chitosan and starch reinforce the films. ► Water vapor permeability of films is decreased by these low chitosan concentration. ► The constrained mixtures design was useful for this study.
Films composed of cassava starch, chitosan and glycerol were produced by blown extrusion and employing a design for constrained surfaces and mixtures. The effects of the components of the mixture on the mechanical properties, water vapor permeability (WVP) and opacity of the films were studied. According to the models generated by the design, the concentration of starch had a positive effect in all properties. The plasticizer glycerol and its interactions with other components had a positive effect on increasing the WVP. The presence of a higher relative concentration of chitosan favored the formation of more rigid and opaque and less permeable films. In general, the concentrations of starch, chitosan and glycerol led to changes in the film properties, potentially affecting their performance. The design for constrained surfaces and mixtures proved to be a useful tool for this type of study due to the complexity of the conditions of film formation.
Green synthesis is one of the most valuable and emerging methods for the synthesis of nanoparticles (NPs) nowadays, presenting imperative biological benefits, reduced process time, ...cost-effectiveness, and environmental benefits, as an alternative to physical and chemical processes. Silver, a noble metal, possess unique properties and potential applications in medicine, requiring the search for novel and suitable tools for its production due to the growing demand. The exploration of plants diversity can be used towards rapid and single-step preparatory methods for various NPs, maintaining the green principle over conventional ones, an important aspect for medical applications. Plants contain bio-organics components, which usually play multiple roles as reducing, capping as well as stabilizing agents for metal compounds into silver nanoparticles (AgNPs). The stability of these NPs is governed by certain parameters, which influence stability and bioavailability. In this perspective, this review aims to provide a comprehensive view to understand the possible induced mechanism, current scenario and future prospects for the bio-inspired synthesis of AgNPs.
New biodegradable trays based on cassava starch blended with sugarcane bagasse (SB), as the main component, and cornhusk (CH), malt bagasse (MB), or orange bagasse (OB) have been investigated. ...Gelatinized cassava starch solution was used as binder. The resulting trays displayed thickness between 3.505 ± 0.18 and 3.964 ± 0.52 mm and density between 0.199 ± 0.01 and 0.213 ± 0.02 g/cm3. All the biodegradable trays presented high water sorption capacity during storage under high or medium relative humidity. Mechanical analyses revealed that addition of different amounts of agroindustrial residues (CH, MB, or OB) to the materials affected resistance, making the biodegradable trays more rigid than EPS trays. Biodegradability tests demonstrated that all the trays fabricated from agroindustrial residues were more susceptible to degradation. Trays containing over 20% OB were completely degraded within 60 days. In conclusion, fibrous agroindustrial residues can be potentially employed to produce biodegradable trays, especially the combination of sugarcane bagasse and cornhusk.
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•Trays containing sugarcane and malt or orange bagasse or cornhusk were prepared.•All the biodegradable trays were more rigid than traditional EPS trays.•Addition of 20 and 30% MB or OB produced less mechanically resistant trays.•Trays stored under medium and high relative humidity had high water sorption.•After analysis for 60 days, trays with 20 or 30% OB were completely degraded.
Due to market demand for natural products, the problems associated with climate change, and the limitations associated with chemical extraction processes, the use of biotechnological processes has ...attracted more attention as an alternative method of obtaining commercial products. These methods are applicable in the pharmaceutical, textile, and, especially, in the food sector. Companies such as Novozyme, DuPont, BASF SE, Evonik Industries AG and DSM, and several others have invested in the biotechnology sector in order to obtain new methods to optimize these processes, as well as to develop products of commercial interest (e.g. enzymes, polysaccharides, pigments, organic acids, flavors, and surfactants). Thus, there is great importance in the development of bioprocesses, from the selection of microorganisms to the optimization and elevation of the fermentative scale. The overall aim is the establishment of viable processes for obtaining industrial products for the food industry.
