Effect of viscosity-inducing factors on oxygen transfer in production culture of bacterial cellulose

Enhanced bacterial cellulose production by Komagataeibacter species and Hibiscus sabdariffa herbal tea

This study proposed Hibiscus sabdariffa as a novel substrate for BC production with Komagataeibacter species and their consortia. K. intermedius is found as the most efficient producer (5.98 g/L BC, 3.56 × 10-2 g-1 h-1 productivity rate) following K. maltaceti (4.44 g/L BC, 2.64 × 10-2 g-1 h-1 productivity rate) and K. nataicola (3.67 g/L BC, 2.18 × 10-2 g-1 h-1 productivity rate). Whereas agitation increased BC production with K. nataicola (1.22-fold, 4.49 g/L BC), K. maltaceti (1.24-fold, 5.52 g/L BC) and K. intermedius (1.27-fold, 7.63 g/L BC), irregular shaped BC was obtained. This could be a novel result as Komagataeibacter consortia increased BC production by 1.17-2.01-fold compared to monocultures resulting as 8.11 g/L BC through the co-cultivation of K. maltaceti-K. intermedius. Maximum increase was found to be 1.75-fold (1.79-fold WHC), occurring with monoculture of K. maltaceti, while 1.94-fold (1.26-fold WHC) with K. maltaceti-K. intermedius consortium when H. sabdariffa-based media compared Hestrin-Schramm media. Based on these results, this could be a novel result as H. sabdariffa-based media may replace the use of HS media in BC production by means of a bioactive content-rich plant and obtaining 3-D ultrafine porous structure with high thermal resistant (∼460-500 °C) BC with mono and co-cultivation of Komagataeibacter species to be used in industrial area.

Enhanced bacterial cellulose production in Gluconacetobacter xylinus by overexpression of two genes (bscC and bcsD) and a modified static culture

Bacterial cellulose (BC), a nanostructured material, is renowned for its excellent properties. However, its production by bacteria is costly due to low medium utilization and conversion rates. To enhance the yield of BC, this study aimed to increase BC yield through genetic modification, specifically by overexpressing bcsC and bcsD in Gluconacetobacter xylinus, and by developing a modified culture method to reduce medium viscosity by adding water during fermentation. As a result, BC yields of 5.4, 6.2, and 6.8 g/L were achieved from strains overexpressing genes bcsC, bcsD, and bcsCD, significantly surpassing the yield of 2.2 g/L from wild-type (WT) strains. In the modified culture, the BC yields of all four strains increased by >1 g/L with the addition of 20 mL of water during fermentation. Upon comparing the properties of BC, minimal differences were observed between the WT and pbcsC strains, as well as between the static and modified cultures. In contrast, BC produced by strains overexpressing bcsD had a denser microstructural network and exhibited demonstrated higher tensile strength and elongation-to-break. Compared to WT, BC from bcsD overexpressed strains also displayed enhanced crystallinity, higher degree of polymerization and improved thermal stability.

Bacterial cellulose: Strategies for its production in the context of bioeconomy

Bacterial cellulose has advantages over plant-derived cellulose, which make its use for industrial applications easier and more profitable. Its intrinsic properties have been stimulating the global biopolymer market, with strong growth expectations in the coming years. Several bacterial species are capable of producing bacterial cellulose under different culture conditions; in this context, strategies aimed at metabolic engineering and several possibilities of carbon sources have provided opportunities for the bacterial cellulose's biotechnological exploration. In this article, an overview of biosynthesis pathways in different carbon sources for the main producing microorganisms, metabolic flux under different growth conditions, and their influence on the structural and functional characteristics of bacterial cellulose is provided. In addition, the main industrial applications and ways to reduce costs and optimize its production using alternative sources are discussed, contributing to new insights on the exploitation of this biomaterial in the context of the bioeconomy.

A novel static cultivation of bacterial cellulose production from sugar beet molasses: Series static culture (SSC) system

In bacterial cellulose (BC) production, we developed a new static cultivation system named series static culture (SSC) to eliminate air limitation problem encountered in conventional static culture (CSC). In SSC system, the fermentation broth at the bottom of BC pellicle produced in initial culture medium is transferred to the next empty sterile culture medium at the end of a certain fermentation period. This procedure was performed until BC production ceased. Fermentation experiments were carried out using Gluconacetobacter xylinus NRRL B-759 and sugar beet molasses at 30 °C and initial pH 5. Also, some quality parameters of produced BC pellicles were determined. Final pH at the stages of SSC system was higher that of the initial pH due to sugar content (sucrose) of molasses and microorganism used. Total BC production increased with increasing sugar concentration in SSC. As a result, an increase of 22.02 % in BC production was achieved using developed SSC. FT-IR spectra of all BC pellicles produced were typical spectra. The absorption bands at the relevant wavenumbers identify the mode of vibrations of the created chemical bonds arising at the BC surface such as OH, CH, H-O-H, C-O-C, and C-OH. XRD analyses showed that the crystallinity index values of BC obtained from CCS and SSC were high. The form of produced all BC pellicles is generally Cellulose I. Removal of surface moisture and depolymerisation of carbon skeleton were determined from TGA-DTA thermograms. SEM images showed that the BC samples produced had nano-sized cellulose fibrils which were aggregated in fermentation media containing molasses. Finally, the BC samples, especially in molasses media, having high mechanical strength and WHC were found.

Bacterial Cellulose Cultivations Containing Gelatin Form Tunable, Highly Ordered, Laminae Structures with Fourfold Enhanced Productivity

Manipulation of bacterial cellulose (BC) morphology is important to tune BC properties to meet specific application requirements. In this study, gelatin was added to cultivation media at 0.1-7.5 wt %. After cultivations, gelatin was removed from the BC matrix, and its effects on BC matrix characteristics and fermentation production efficiency were determined. Higher contents of gelatin in cultivation media (up to 5%) resulted in BC that, from scanning electron microscopy observations, had larger pore sizes and formation of a lamina morphology that was highly unidirectional. Crystallinity remained unchanged between 0.1 and 5 wt % gelatin concentrations (92-95%); however, it decreased to 86% at a gelatin concentration of 7.5 wt %. Mechanical properties showed a positive trend as both the specific modulus and specific strength values increased as the gelatin concentration increased to 5 wt %. A breakdown in the ordered structure of the BC matrix occurs at 7.5 wt % gelatin, with corresponding decreases in the specific modulus and specific strength of the BC. The productivity increased by almost 4-fold relative to the control, reaching 1.64 g·L^-1h^-1 at the 2.5 wt % gelatin content. Also, the water holding capacity increased by 3-fold relative to the control, reaching 306.6 g of water per g BC at the 5.0 wt % gelatin content. The changes observed in these BC metrics can be explained based on literature findings associated with the formation of gelatin aggregates in the cultivation media and an increase in gel stiffness seen at higher media gelatin concentrations. Overall, this work provides a roadmap for manipulating BC properties while creating highly organized lamina morphologies.

Biomedical engineering aspects of nanocellulose: a review

Cellulose is one of the most abundant renewable biopolymer in nature and is present as major constituent in both plant cell walls as well as synthesized by some microorganisms as extracellular products. In both the systems, cellulose self-assembles into a hierarchical ordered architecture to form micro to nano-fibrillated structures, on basis of which it is classified into various forms. Nanocellulose (NCs) exist as rod-shaped highly crystalline cellulose nanocrystals to high aspect ratio cellulose nanofibers, micro-fibrillated cellulose and bacterial cellulose (BC), depending upon the origin, structural and morphological properties. Moreover, NCs have been processed into diversified products ranging from composite films, coatings, hydrogels, aerogels, xerogels, organogels, rheological modifiers, optically active birefringent colored films using traditional-to-advanced manufacturing techniques. With such versatility in structure-property, NCs have profound application in areas of healthcare, packaging, cosmetics, energy, food, electronics, bioremediation, and biomedicine with promising commercial potential. Herein this review, we highlight the recent advancements in synthesis, fabrication, processing of NCs, with strategic chemical modification routes to tailor its properties for targeted biomedical applications. We also study the basic mechanism and models for biosynthesis of cellulose in both plant and microbial systems and understand the structural insights of NC polymorphism. The kinetics study for both enzymatic/chemical modifications of NCs and microbial growth behavior of BC under various reactor configurations are studied. The challenges associated with the commercial aspects as well as industrial scale production of pristine and functionalized NCs to meet the growing demands of market are discussed and prospective strategies to mitigate them are described. Finally, post chemical modification evaluation of biological and inherent properties of NC are important to determine their efficacy for development of various products and technologies directed for biomedical applications.

Proteomic analysis of secretomes from Bacillus sp. AR03: characterization of enzymatic cocktails active on complex carbohydrates for xylooligosaccharides production

Bacillus sp. AR03 have been described as an important producer of carbohydrate-active enzymes (CAZymes) when growing in a peptone-based medium supplemented with simple sugars and/or carboxymethyl cellulose (CMC) as carbon sources. This work aimed to identify the extracellular enzymatic cocktails through shotgun proteomics. The proteomic analysis showed that enzymes involved in cellulose and xylan degradation were among the most abundant proteins. These enzymes included an endo-glucanase GH5_2 and a glucuronoxylanase GH30_8, which were found in all conditions. In addition, several proteins were differentially expressed in the three evaluated culture media, indicating microbial metabolic changes due to the different supplied carbon sources, particularly, in the presence of CMC. Finally, the capability of the crude enzymatic cocktails from culture media to degrade birchwood xylan was assessed, which produced mostly xylooligosaccharides containing among 3-5 xylose units. Consequently, this work shows the potential of the extracellular enzymes from Bacillus sp. AR03 for producing emergent prebiotics.

Lignocellulosic Biomass for the Synthesis of Nanocellulose and Its Eco-Friendly Advanced Applications

Nanocellulose is a unique and natural compound extracted from native cellulose using different extraction techniques. Nanocellulose is currently attracting attention due to its excellent properties such as special surface chemistry, exceptional physical and chemical strength, and rich hydroxyl groups for modification. In addition, its significant biological properties, like biodegradability, biocompatibility, and non-toxicity, accompanied by being environmentally friendly, are added advantages. The current review is focused on the lignocellulosic biomass processing methods for nanocellulose production and their usage for eco-friendly and environmental sustainability. We have also described insights into different techniques by which cellulosic materials can be changed into cellulose nanofibers (CNFs) and cellulose nanocrystals (CNCs). Lastly, we further discussed how nano-cellulosic materials are being used in a variety of industries such as the food sector, biomedical hygiene products, health care, water purification, and sensors. In the review, the unique uses of nanocelluloses in the production of nanocomposite materials, like flexible supercapacitor and polymer matrix, toward minimizing the utilization of global fossil energy and environmental pollution are envisaged. Finally, the significant application of nanomaterials in the areas of packaging industries, health and hygienic sector, cosmetics, and other important sectors are discussed. In the aspect of techno-economically feasibility, nano-cellulose-based materials may prove to be outstanding, environment friendly, and mitigate effluent load.

Bacterial nanocellulose: Present status, biomedical applications and future perspectives

Bacterial nanocellulose (BNC) has emerged as a natural biopolymer of significant importance in diverse technological areas due to its incredible physicochemical and biological characteristics. However, the high capital investments, production cost and lack of well-organized scale-up processes resulting in low BNC production are the major impediments need to be resolved. This review enfolds the three different and important portions of BNC. Firstly, advancement in production technologies of BNC like cell-free extract technology, static intermittent fed batch technology and novel cost-effective substrates that might surmount the barriers associated with BNC production at industrial level. Secondly, as BNC and its composites (with other polymers/nanoparticles) represents the utmost material of preference in current regenerative and diagnostic medicine, therefore recently reported biomedical applications of BNC and functionalized BNC in drug delivery, tissue engineering, antimicrobial wound healing and biosensing are widely been focused here. The third and the most important aspect of this review is an in-depth discussion of various pitfalls associated with BNC production. Recent trends in BNC research to overcome the existing snags that might pave a way for industrial scale production of BNC thereby facilitating its feasible application in various fields are highlighted.

Production, characterization and biological features of bacterial cellulose from scum obtained during preparation of sugarcane jaggery (gur)

Bacterial cellulose (BC) has been given an ample attention due to its high potential for many industrial applications. However, the high cost of production medium has hindered the commercialization of BC. Several efforts have been made to explore cheep, raw and waste sources for BC production. The current study aims at investigating the BC production from a waste source; the scum obtained during preparation of sugarcane jaggery or gur (JS). JS was five-fold diluted with distilled water and used as culturing medium without any additional nutrients. The production of BC was monitored till 10th days of cultivation both at static and shaking culturing conditions. A maximum of 2.51 g/L and 2.13 g/L BC was produced in shaking and static cultures, respectively, after 10 days. The structure features of BC were confirmed through FTIR, XRD and SEM analysis. The chemical structure and physical appearance strongly resembled the BC produced form synthetic media. It was noteworthy that the BC produced from JS showed higher mechanical and thermal properties. The cell adhesion and proliferation capabilities of produced BC were observed that depicted definite animal cell adhesion without any considerable cytotoxicity. Besides providing an economically feasible way for BC production, the high level of physico-mechanical and biological properties insured the importance in medical fields.