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Biocompatibility of levan samples recovered from medium with/without industrial boric acid on L929 mouse fibroblast cells. Cells were treated with 100–1000 µg/mL of levan for 24 h. In the figure, w with industrial boric acid, w/o without industrial boric acid
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Levan polysaccharide is an industrially important natural polymer with unique properties and diverse high-value applications. However, current bottlenecks associated with its large-scale production need to be overcome by innovative approaches leading to economically viable processes. Besides many mesophilic levan producers, halophilic Halomonas smy...
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Natural biopolymers have gained worldwide importance as multipurpose polysaccharides. The demand for natural polymers by different industries around the world is increasing day by day, leading to new avenues in research on microbial exopolysaccharides (EPS). Current study attempted for the isolation of dextran producing microorganisms from indigeno...
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... This is consistent with the known induction of bacterial metabolic pathways exclusively by sucrose availability in the culture medium. Typically, the microbial levan is released into the culture medium and recovered through alcoholic precipitation of cell-free supernatant [5][6][7][8][9][10]. The levan produced by strain 2ASCA showed a new attribute in that the polymer was associated with cells and did not dissolve in broth culture. ...
... In the literature, there are reports that demonstrate that agro-industrial byproducts such as beet molasses, sugar cane molasses, and syrup have been used as alternative carbon sources and have allowed for adequate microbial growth and EPS production via SmF [26,41]. Levan is an EPS with a high potential to be used in various industries given its physicochemical and functional characteristics [24,42]; however, to improve performance and quality, the design of a process allowing for large-scale, efficient, ecological, and profitable production is necessary [7,21]. Because of this, the objective of the present work was to evaluate the EPS production potential of the indigenous yeast strain Suhomyces kilbournensis under different process conditions. ...
The valorization of byproducts from the sugarcane industry represents a potential alternative method with a low energy cost for the production of metabolites that are of commercial and industrial interest. The production of exopolysaccharides (EPSs) was carried out using the yeast Suhomyces kilbournensis isolated from agro-industrial sugarcane, and the products and byproducts of this agro-industrial sugarcane were used as carbon sources for their recovery. The effect of pH, temperature, and carbon and nitrogen sources and their concentration in EPS production by submerged fermentation (SmF) was studied in 170 mL glass containers of uniform geometry at 30 °C with an initial pH of 6.5. The resulting EPSs were characterized with Fourier-transform infrared spectroscopy (FT-IR). The results showed that the highest EPS production yields were 4.26 and 44.33 g/L after 6 h of fermentation using sucrose and molasses as carbon sources, respectively. Finally, an FT-IR analysis of the EPSs produced by S. kilbournensis corresponded to levan, corroborating its origin. It is important to mention that this is the first work that reports the production of levan using this yeast. This is relevant because, currently, most studies are focused on the use of recombinant and genetically modified microorganisms; in this scenario, Suhomyces kilbournensis is a native yeast isolated from the sugar production process, giving it a great advantage in the incorporation of carbon sources into their metabolic processes in order to produce levan sucrose, which uses fructose to polymerize levan.
... Specific wild bacteria species that produce levan include Bacillus subtilis (Natto), Bacillus licheniformis ANT 179, Bacillus licheniformis BK AG21, Brachybacterium sp. CH-KOV3, Geobacillus stearothermophilus, Halomonas smyrnensis AAD6T, Lactobacillus reuteri strain 121, Paenibacillus polymyxa EJS-3, Streptococcus salivarius SS2, and Zymomonas mobilis [83,101,[109][110][111][112][113][114][115][116]. ...
Fructans are fructose-based polymers, defined as fructooligosaccharides (FOS), when they possess a short chain. These molecules are highly appreciated in the food and pharmaceutical international market and have an increasing demand worldwide, mainly for their prebiotic activity and, therefore, for all their health benefits to those who consume them constantly. Thus, new natural or alternative FOS production systems of industrial scale are needed. In this regard, microorganisms (prokaryotes and eukaryotes) have the potential to produce them through a wide and diverse number of enzymes with fructosyltransferase activity, which add a fructosyl group to sucrose or FOS molecules to elongate their chain. Microbial fructosyltransferases are preferred in the industry because of their high FOS production yields. Some of these enzymes include levansucrases, inulosucrases, and β-fructofuranosidases obtained and used through biotechnological tools to enhance their fructosyltransferase activity. In addition, characterizing new microorganisms with fructosyltransferase activity and modifying them could help to increase the production of FOS with a specific degree of polymerization and reduce the FOS production time, thus easing FOS obtention. Therefore, the aim of this review is to compile, discuss, and propose new perspectives about the microbial potential for FOS production through enzymes with fructosyltransferase activity and describe the modulation of FOS production yields by exogenous stimuli and endogenous modifications.
... The maximum levan production of 59.5 g/L is obtained in 16 L bioreactor [13]. The levan production of 18 g/L by Halomonas smyrnensis was achieved using inexpensive and alternative industrial medium components in a 5-L bioreactor system under non-sterile conditions [32]. On comparison of the results from the other researches clearly reveals the high levan yield in 5 L bioreactor with 80 g/L cane molasses as substrate. ...
This study investigated the production of levan biopolymer utilizing cane molasses, an agro-industrial waste, as a substrate. The kinetics of growth, substrate consumption, and levan production by Bacillus megaterium KM3 were examined in bioreactor design employing cane molasses-based media. Experiments were conducted in triplicate to ensure reproducibility, first in a 1L shake flask under optimized conditions, followed by scale-up to a 5L bioreactor, achieving a maximum levan yield as 18.5 g/L. The logistic model for microbial growth and Luedeking–Piret equation for product formation and substrate utilization were found to fit the experimental data, with a maximum specific growth rate constant (µm) as 0.6 h⁻¹. The obtained levan was purified, and monosaccharide analysis by HPLC, confirmed the presence of the fructose monomer. Further structural characterization for the presence of functional group was performed using FTIR. Congo red analysis reveals a triple-helix structure. XRD analysis indicated the levan’s non-crystalline amorphous nature, while thermogravimetric analysis demonstrated its high thermal stability. In addition, the in vitro biological activity of levan was evaluated, where it showed strong antioxidant activities to scavenge DPPH radical, hydroxyl radical, and reducing power in dose-dependent manner. The results showcased the promising structural and functional properties of the obtained levan, positioning it as an attractive biopolymer for a wide range of industrial applications. By turning trash into gold, this study provides a model of clean technology’s potential to boost productivity while simultaneously lessening its negative effects on the environment.
Graphical Abstract
... Gan et al. (2022) mentioned that pullulan/CS can be combined with LVN. In our study, LVN was extracted from Halomonas smyrnensis by using the method explained previously by Erkorkmaz et al. (2018). Apart from the several advantages of LVN, it has not been used as an edible film treatment in combination with mucilage on tomatoes. ...
Tomato is among the most important parts of the human diet globally. However, due to its short shelf life, the produce faces the non-desired huge postharvest losses that can be ascribed to high ethylene emission, high respiration rate, and weight loss. Conventional approaches used to enhance the shelf life of cocktail tomatoes come with certain disadvantages such as chilling injury and investment cost. This study aimed to investigate the effects of bio-based coatings on the shelf life of cocktail tomatoes. The breaker stage tomato fruit were treated with chitosan (CS), chitosan+levan (CS-LVN), chitosan+mucilage (CS-MCLG), and chitosan+ mucilage+levan (CS-MCLG-LVN) edible coatings. Control (CTL) fruit received no treatment. Tomatoes were kept in cold storage (CST) for 30 days (d) at 10 °C temperature and 90–95% relative humidity (RH). At every removal, the fruit was kept for an additional 3 d at 20 °C and 60 ± 5% RH to determine the shelf life (SL) performance. Edible coating treatments minimized the weight loss, ethylene emission, respiration rate, and amount of unmarketable fruit and slowed down the synthesis of lycopene. The minimum weight losses and amount of unmarketable fruit were determined in the CS-MCLG-LVN coating treatment. CS-MCLG-LVN and CS-MCLG-treated fruit had the lowest ethylene emission and respiration rates. CS coating treatment manifested the highest L* value and malic acid content while the maximum total phenolic and total flavonoid contents were in CS-LVN. It can be concluded that CS-LVN, CS-MCLG, and CS-MCLG-LVN edible coatings maintained the postharvest quality of tomatoes for 30 d.
https://doi.org/10.1016/j.scienta.2023.112500
... In recent years, other studies have explored alternative uses of molasses as a sucrose source for levan production, employing strains such as B. lentus V8 [75] or Brachybacterium phenoliresistens, where molasses and date syrup have been used [76]. Another solution to the challenge of searching for substitutes for culture medium substrates is the process described by Erkorkmaz et al., in which the growth and yielding of levan by Halomonas smyrnensis was compared in a medium containing industrial sucrose from sugar beet syrup, salts of various origins as well as three different industrial boron compounds [77]. The most optimal culture medium, consisting of industrial food sucrose from sugar beets, sea salt from Çamaltı, industrial boric acid and borax pentahydrate, yielded 18.60 g/L levan, which is the highest yield recorded for H. smyrnensis to date [77]. ...
... Another solution to the challenge of searching for substitutes for culture medium substrates is the process described by Erkorkmaz et al., in which the growth and yielding of levan by Halomonas smyrnensis was compared in a medium containing industrial sucrose from sugar beet syrup, salts of various origins as well as three different industrial boron compounds [77]. The most optimal culture medium, consisting of industrial food sucrose from sugar beets, sea salt from Çamaltı, industrial boric acid and borax pentahydrate, yielded 18.60 g/L levan, which is the highest yield recorded for H. smyrnensis to date [77]. Levan is a multifunctional polymer of great industrial importance; hence, microorganisms characterized by its increased synthesis are still being sought. ...
Polysaccharides are essential components with diverse functions in living organisms and find widespread applications in various industries. They serve as food additives, stabilizers, thickeners, and fat substitutes in the food industry, while also contributing to dietary fiber for improved digestion and gut health. Plant-based polysaccharides are utilized in paper, textiles, wound dressings, biodegradable packaging, and tissue regeneration. Polysaccharides play a crucial role in medicine, pharmacy, and cosmetology, as well as in the production of biofuels and biomaterials. Among microbial biopolymers, microbial levan, a fructose polysaccharide, holds significant promise due to its high productivity and chemical diversity. Levan exhibits a wide range of properties, including film-forming ability, biodegradability, non-toxicity, self-aggregation, encapsulation, controlled release capacity, water retention, immunomodulatory and prebiotic activity, antimicrobial and anticancer activity, as well as high biocompatibility. These exceptional properties position levan as an attractive candidate for nature-based materials in food production, modern cosmetology, medicine, and pharmacy. Advancing the understanding of microbial polymers and reducing production costs is crucial to the future development of these fields. By further exploring the potential of microbial biopolymers, particularly levan, we can unlock new opportunities for sustainable materials and innovative applications that benefit various industries and contribute to advancements in healthcare, environmental conservation, and biotechnology.
... The enzyme's activity was controlled by the ionization state of its amino acids, which was influenced by the pH of the medium to which it was exposed [5]. Erkorkmaz et al. [35] expressed identical findings, indicating that H. smyrnensis AAD6T reached its greatest biomass and levan titer at an initial pH value of 7.0. Moussa et al. [16] experimented to determine the optimal pH for levan synthesis using several values (7, 7.5, 7.8, 8, and 8.5). ...
Levan is a homopolysaccharide of fructose units that repeat as its structural core. As an exopolysaccharide (EPS), it is produced by a great variety of microorganisms and a small number of plant species. The principal substrate used for levan production in industries, i.e., sucrose, is expensive and, hence, the manufacturing process requires an inexpensive substrate. As a result, the current research was designed to evaluate the potential of sucrose-rich fruit peels, i.e., mango peels, banana peels, apple peels, and sugarcane bagasse, to produce levan using Bacillus subtilis via submerged fermentation. After screening, the highest levan-producing substrate, mango peel, was used to optimize several process parameters (temperature, incubation time, pH, inoculum volume, and agitation speed) employing the central composite design (CCD) of response surface methodology (RSM), and their impact on levan production was assessed. After incubation for 64 h at 35 °C and pH 7.5, the addition of 2 mL of inoculum, and agitation at 180 rpm, the highest production of levan was 0.717 g/L of mango peel hydrolysate (obtained from 50 g of mango peels/liter of distilled water). The F-value of 50.53 and p-value 0.001 were calculated using the RSM statistical tool to verify that the planned model was highly significant. The selected model’s accuracy was proven by a high value (98.92%) of the coefficient of determination (R2). The results obtained from ANOVA made it clear that the influence of agitation speed alone on levan biosynthesis was statistically significant (p-value = 0.0001). The functional groups of levan produced were identified using FTIR (Fourier-transform ionization radiation). The sugars present in the levan were measured using HPLC and the levan was found to contain only fructose. The average molecular weight of the levan was 7.6 × 106 KDa. The findings revealed that levan can be efficiently produced by submerged fermentation using inexpensive substrate, i.e., fruit peels. Furthermore, these optimized cultural conditions can be applied on a commercial scale for industrial production and commercialization of levan.
... Many bacteria are capable of synthesizing levan, including Gram-negative bacteria of the class Alphaproteobacteria, Acetobacter, Gluconobacter [224][225][226], Komagataeibacter (Gluconacetobacter) [227], and Zymomonas [228][229][230] genera, and those of the class Gammaproteobacteria, Pseudomonas [231], Halomonas [232,233], and Erwinia [234] genera, as well as Gram-positive bacteria of the class Bacilli: Bacillus [235][236][237][238][239][240][241][242][243][244][245], Paenibacillus [246][247][248][249][250][251][252][253][254][255][256][257][258][259][260], Lactobacillus [261], Leuconostoc [262] genera, etc. Currently, more than 100 bacteria species have been shown to produce levan [222]. ...
... The good levan producer Pseudomonas fluorescens strain ES, with promising antioxidant and cytotoxic activity against different kinds of cancer cells, was isolated from soil in Egypt [231]. Possible levan producers were also identified among Gram-negative halophilic Gammaproteobacteria of the Halomonas genus [232] including Halomonas smyrnensis AAD6 T [233]. Their ability to grow in high concentrations of NaCl can be used to solve the problem of sterility in an industrial setting. ...
Bacterial exopolysaccharides (EPS) are essential natural biopolymers used in different areas including biomedicine, food, cosmetic, petroleum, and pharmaceuticals and also in environmental remediation. The interest in them is primarily due to their unique structure and properties such as biocompatibility, biodegradability, higher purity, hydrophilic nature, anti-inflammatory, antioxidant, anti-cancer, antibacterial, and immune-modulating and prebiotic activities. The present review summarizes the current research progress on bacterial EPSs including their properties, biological functions, and promising applications in the various fields of science, industry, medicine, and technology, as well as characteristics and the isolation sources of EPSs-producing bacterial strains. This review provides an overview of the latest advances in the study of such important industrial exopolysaccharides as xanthan, bacterial cellulose, and levan. Finally, current study limitations and future directions are discussed.
... The obtained chia gel was stored at 4 ± 1 • C for further experiments. Levan was produced through microbial fermentation of Halomonas smynensis AAD6 T under controlled bioreactor conditions and purified from the cell-free culture medium as described previously (Erkorkmaz et al., 2018). ...
Sweet cherry (Prunus avium L.) fruits are prone to quality and quantity loss in shelf-life conditions and cold storage due to their short post-harvest life. Until now efforts have been made to extend the shelf life of the sweet cherry. However, an efficient and commercially scalable process remains elusive. To contribute to this challenge, here in this study, biobased composite coatings consisting of chitosan, mucilage, and levan, were applied on sweet cherry fruits and tested for postharvest parameters in both market and cold storage conditions. Results demonstrated that the shelf life of sweet cherries can be extended until the 30th day while retaining important post-harvest properties like decreased weight loss, fungal deterioration, increased stem removal force, total flavonoid, L-ascorbic acid, and oxalic acid. Given the cost-effectiveness of the polymers used, the findings of this study indicate the feasibility of extending the shelf-life of sweet cherries on a larger scale.
... The highest yield of levan reached 18.06 g/l [117] Trends in Biotechnology ...
Microbial biomanufacturing, powered by the advances of synthetic biology, has attracted growing interest for the production of diverse products. In contrast to conventional microbes, extremophiles have shown better performance for low-cost production owing to their outstanding growth and synthesis capacity under stress conditions, allowing unsterilized fermentation processes. We review increasing numbers of products already manufactured utilizing extremophiles in recent years. In addition, genetic parts, molecular tools, and manipulation approaches for extremophile engineering are also summarized, and challenges and opportunities are predicted for non-conventional chassis. Next-generation industrial biotechnology (NGIB) based on engineered extremophiles promises to simplify biomanufacturing processes and achieve open and continuous fermentation, without sterilization, and utilizing low-cost substrates, making NGIB an attractive green process for sustainable manufacturing.
