Biopolymer

This paper presents a review of the chemical, physical and morphological characteristics, as well as the existing applications and mechanisms for the production of poly (3-hydroxybutyrate). This biopolymer, which is obtained from renewable sources, degrades when exposed in biologically active environments and is biocompatible, that is, it is not rejected by the human body in health applications. However, in spite of presenting similar properties with some conventional plastics, the PHB exhibits fragile behavior and thermal instability when processed. The literature proposes the use of blends, the development of copolymers or the insertion of additives in an attempt to improve the mechanical and thermal properties of PHB.

Plastic industry is one of the vastly growing industries in the world, but due to its negative environmental impact, the incorporation of biodegradable polymer in such industry becomes a must. Albeit the high production cost; Microbial polymer was proven to be the most potential polymer to be used in the biodegradable polymer industry. An Egyptian local bacterial strain, identified as Microbacterium sp.WA81, was able to produce approximately 18 mg/L of the polymer. The proposed isolate could be considered as a novel species; as none of the closest type strain was reported to accumulate biopolymers. The produced polymer was extracted, purified and characterized; showing highly desirable characteristics including the relatively low molecular weight which is advantageous property. In order to reduce the production cost; a number of local cheap materials were screened using 2-level Fractional Factorial Design reporting that Molasses, Whey and Ground Sesame to be the most potential media components for maximizing the productivity by the local bacterial isolate. A subsequent Response Surface Methodology algorithm was applied to determine the exact optimum combination to maximize the polymer productivity by converting industrial by-products into value-added ones. Depending on the generated mathematical model, the optimum combination was determined to be 9.21 g/L, 8.49 g /L and 8.12 g/L for Molasses, Whey and Ground Sesame respectively leading to a remarkable increase in polymer productivity (up to 660 mg/L). On the transfer of this process to the bioreactor cultivation level, under precise controlled conditions, the amount of the polymer produced was increased up to 2.5 g/L achieving more than 250% increase compared to the amount produced prior to optimization. The data concluded that application of the 2-level fractional factorial design and the Response Surface Methodology algorithm are very useful in optimizing polymer production by this local bacterial isolate.

Special Issue "Sustainable Fermentation Technology"
New Special Issue, entitled “Sustainable Fermentation Technologies” has been launched in the Sustainability Journal. The proposed Special Issue on “Sustainable Fermentation Technologies” aims to disseminate recent innovative research regarding the emerging role of fermentation and relevant technological developments in the efficient utilization of the abovementioned renewable raw materials for the production of the variety of high-value biobased products discussed above. This Special Issue also aims to highlight the key challenges that arise in this demanding research area.
The topics of interest include (but are not limited to) the following potential application of fermentation technologies in:
1. Production of biofuels including liquid fuels (bioethanol, biobutanol, biomethanol, biopropanol/isopropanol) and gaseous biofuels, including biohydrogen (hydrogen generation by photo fermentation and dark fermentation), and biogas (biomethane generated through anaerobic fermentation)
2. Production of industrially important biochemicals, such as biopolymers, bioplastics biosurfactants, xylitol, dyes and pigments, lipids, proteins, organic acids (lactic, acetic, propionic, butyric, succinic), and solvents (acetone)
3.Production of chemicals known as molecules with multiple active groups, such as diols, diamines, dicarboxyacids, and hydroxy fatty acids 4. Production of useful fine chemicals providing the building blocks for many different products, such as pharmaceuticals, biocides, fragrances, and additives
5.Production of biomolecules known as biologically active compounds with potential applications in medicine and pharmaceutical products and food industry such as carbohydrates, polyphenols, carotenoids, phytosterols, and fatty acids
6. Fermentation-mediated wastewater treatment for production biochemicals and value-added products The Special Issue considers original research articles, short communications, reviews, mini-reviews, and case studies that make a significant contribution in the field of sustainable fermentation technology.
Manuscript Submission Information Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website. Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sustainability is an international peer-reviewed open access semimonthly journal published by MDPI. Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions. This special issue is now open for submission.

Keywords: fermentation technology biomass feedstock, biowastes sustainability biofuels, value-added products, bioactive compounds, chemical building blocks, biopolymers, biomaterials

We look forward to receiving your high-quality research.
Prof. Dr. Silvio Silvério da Silva
Dr. Peyman Abdeshahian
Dr. Felipe Antonio Fernandes Antunes
Dr. Avinash P. Ingle
Guest Editors

At present, most development work on plastic materials has been focused on the application of biodegradable materials, especially poly(lactic acid)(PLA). PLA is gaining popularity due to its renewability and comparable properties with petroleum-based polymers 1. Similar to PLA, natural rubber is derived from renewable sources and can be processed using the most conventional polymer processing equipment. PLA is a brittle thermoplastic with high strength and modulus 2 , while NR is ductile with a lower strength and modulus. In view of their complementary properties, blending PLA with NR is a good choice to improve the properties of PLA, such as toughness and elongation at break without compromising its biodegradability. In contrast, the epoxidised natural rubber (ENR) is a chemically modified form of the cis-1,4-polyisoprene rubber with epoxide groups randomly situated along the polymer backbone 3. The incorporation of ENR into rubber blends offers many advantages, such as improved processability, stiffness, resilience as well as excellent oil resistance, reduced air permeability, good damping and wet grip performance 4,5. Although poly(lactic acid) (PLA) is among widely used biodegradable polymers, it has limited applications due to its inherent brittleness, low elongation at break and toughness. Blending with natural rubber (NR) and epoxidised natural rubber (ENR) seems to be a promising alternative, as both materials are derived from renewable resources. Natural rubber was melt-blended with poly(lactic acid) in an internal mixer, Haake Rheomix, with a rotor speed of 50 r.p.m. at 180ºC. Liquid epoxidised natural rubber (LENR) was used as a compatibiliser in the binary blending system of thermoplastic natural rubber (TPNR). Results indicate that the mixing torque value and stabilisation torque value in LENR blends are lower than in blends without the compatibiliser. Various compositions of natural rubber, epoxidised natural rubber and compatibiliser were investigated with respect to the stress-strain behaviour. It was found that the addition of LENR compatibiliser improved the stress at break and Young's modulus in the blend system of 40/60 PLA/rubber compositions. The increase in stress at break and Young's modulus were associated with the ability of LENR to compatibilise the PLA/NR binary blends.

Soil-based construction materials are of interest as structural building materials due to their green credentials, as well as being present in many historical structures. For effective conservation of the latter, and to motivate greater uptake for new construction, understanding of the mechanical and hydraulic properties of these materials is in need of improvement. Earthen construction materials can be considered to be manufactured unsaturated soils, and advances in understanding can be made by considering them from a geotechnical point of view. This paper presents initial results from a major programme of testing, seeking improved properties for earthen construction materials, where unusual organic compounds have been employed as stabilisers. Two gums (guar and xanthan) used as stabilisers for a soil mixture are shown to have significant effects on certain mechanical properties, some of which can be explained, and other aspects which are in need of further investigation.

Nanocrystalline-cellulose-supported acidic ionic liquid carrying SO 3 H functional group was prepared using nanocrystalline cellulose, imidazole and 1,4-butane sultone as the source chemicals. The prepared nanocrystalline-cellulose-supported ionic liquid catalyst was characterized by AFM and SEM and its catalytic activity in the reaction of resorcinol with ethyl acetoacetate was tested in a solvent-free condition. The effects of reaction time, reaction temperature, and the ratio of catalyst on the conversion of resorcinol were investigated. A variety of coumarin derivatives were obtained in good yield in the absence of solvent.

In an attempt to increase the bioactivity and corrosion resistance of a Ti–6Al–4V alloy, the thermochemical process for surface modification was utilized. Ti6Al4V substrates were pretreated with a sodium hydroxide (10 M of NaOH aqueous solution at 60°C for 24 h.). After NaOH pretreatment, a three-dimensional porous network of hydrogel layer made of sodium titanate was observed on the Ti6Al4V surface. The gel can then be converted to Ti-OH groups during hydrothermal treatment, which will contribute to the formation of hydroxyapatite when immersing them in a simulated body fluid (SBF) solution for 30 days. Characterization was performed by means of X-ray diffraction (XRD), attenuated total Reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), Scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). The resultant apatite layer formed on titanium metal in SBF could enhance the bonding strength between living tissue and the implant.

Epigallocatechin gallate is a type of catechin has many therapeutic advantages, but its scope is limited due to its poor bioavailability. Most of the ingested Epigallocatechin gallate apparently does not get into the blood, since absorption takes place in the small gut and substantial quantities pass from the small intestine to the large intestine, where it undergoes further degradation by the action of local microbiota [1-4]. Chitosan, a polymer of linear polysaccharide, enhances transport of drug across epithelial surfaces and is biocompatible and biodegradable. The aim of this study is to formulate and characterize Epigallocatechin gallate loaded Chitosan nanoparticles prepared by ionic-gelation method. This increases the abosorption and bioavailaility of Epigallocatechin gallate. The resulting nanoparticles tend to aggregate in biological fluid which can be minimized by addition of poloxamer 188. The nanoparticles obtained were evaluated for percentage yield of drug, drug entrapment efficiency, particle size and morphology using scanning electron microscopy (SEM), compatibility studies using Fourier-Transform infrared spectroscopy (FTIR) and Differential scanning calorimetry (DSC) and in vitro release kinetics. Among the four different ratios of drug to polymer, 1:0.5 ratio showed high drug loading and encapsulation efficiency. The resulting nanoparticles were spherical in shape with a smooth surface. The particle size range was 197.84 ± 21.45 nm to 385.45 ± 15.87 nm. The prepared nanoparticles proved to be promising dosage form of Epigallocatechin gallate, with improved bioavailability.

Enhanced oil recovery (EOR) techniques are essential to improve oil production, and polymer flooding has become one of the promising technologies for the Brazilian Pre-Salt scenario. Biopolymers offer a range of advantages considering the Pre-Salt conditions compared to synthetic polymers, such as resistance to high salinity, high temperature, and mechanical degradation. In that sense, bulk rheology is the first step in a workflow for performance analysis. This paper presents a rheological analysis of four biopolymers (Schizophyllan, Scleroglucan, Guar Gum, and Xanthan Gum) in concentrations from 10 to 2,300 ppm, generally suitable for EOR applications, in temperature levels of 25, 40, 50, 60 and 70°C and two brines of 30,100 ppm and 69,100 ppm total dissolved solids, which aim to model seawater and the mixture between injected seawater and reservoir water typical in Pre-Salt conditions. The pseudoplastic behavior, the overlap concentration, and the activation energy were determined for each polymer solution. The structural differences in the polymers resulted in different rheological behaviors. Schizophyllan is the most promising, as its viscosifying power is higher than synthetic polymers comparable to Xanthan Gum. Its resistance at high temperatures is higher than that of synthetic polymers. Scleroglucan behaved similarly to Xanthan Gum, with the added advantage of being nonionic. Guar Gum had the lowest viscosities, highest overlap concentrations, and most pronounced viscosity decay among the tested polymers. To the author's knowledge, rheological studies of the biopolymers presented here, considering the viscosities and the overlap concentration and activation energy, in the Pre-salt conditions, are not available in the literature and this will benefit future works that depend on this information.

The behavior of bovine serum albumin (BSA) in water is scarcely studied, and the thermodynamic properties arising from the
experimental measurements have not been reported. Intrinsic viscosity measurements are very useful in assessing the interaction
between the solute and solvent. This work discussed in a simple determination of the enthalpy of BSA in aqueous solution when the
concentration ranges from 0.2 to 36.71% wt. and the temperature from 35 to 40 ∘
C. The relationship between the concentration and
intrinsic viscosity is determined according to the method of Huggins. The temperature increase reduces the ratio between inherent
viscosity and concentration (𝜂 𝑖 /𝑐). This is reflected in the Van’t Hoff curve. Furthermore, this work proposes hydrodynamic cohesion
value as an indicator of the degree of affinity of protein with water and thermodynamic implications in conformational changes.