Microbial production of scleroglucan and downstream processing

Abstract

Synthetic petroleum-based polymers and natural plant polymers have the disadvantage of restricted sources, in addition to the non-biodegradability of the former ones. In contrast, eco-sustainable microbial polysaccharides, of low-cost and standardized production, represent an alternative to address this situation. With a strong global market, they attracted worldwide attention because of their novel and unique physico-chemical properties as well as varied industrial applications, and many of them are promptly becoming economically competitive. Scleroglucan, a β-1,3-β-1,6-glucan secreted by Sclerotium fungi, exhibits high potential for commercialization and may show different branching frequency, side-chain length, and/or molecular weight depending on the producing strain or culture conditions. Water-solubility, viscosifying ability and wide stability over temperature, pH and salinity make scleroglucan useful for different biotechnological (enhanced oil recovery, food additives, drug delivery, cosmetic and pharmaceutical products, biocompatible materials, etc.), and biomedical (immunoceutical, antitumor, etc.) applications. It can be copiously produced at bioreactor scale under standardized conditions, where a high exopolysaccharide concentration normally governs the process optimization. Operative and nutritional conditions, as well as the incidence of scleroglucan downstream processing will be discussed in this chapter. The relevance of using standardized inocula from selected strains and experiences concerning the intricate scleroglucan scaling-up will be also herein outlined.

The biopolymer produced by Rhizobium viscosum CECT 908 is a promising agent for application in microbial enhanced oil recovery

“…as the recovery process. The molecular weight calculated for the R. viscosum CECT 908 biopolymer (243.5 ± 16.1 kDa) is in the same range as those reported for scleroglucan or welan gum (100-700 kDa) [4,9,38], but lower compared with those of diutan gum, levan, pullulan or xanthan gum (1,000-50,000 kDa) [9,12,21]. The rheological properties of polymers are affected by their structure and molecular weight.…”

“…The R. viscosum biopolymer remained stable up to 80°C. Other biopolymers such as diutan gum, produced by Sphingomonas spp., or scleroglucan, produced by Sclerotium spp., remained stable up to 90-95°C [12,38]. The viscosity of the biopolymer produced by Pseudomonas oleovorans was significantly reduced when exposed to 100°C for 1 h, but was not affected by temperatures up to 80°C [36,39].…”

“…However, to make it competitive with synthetic polymers, it is necessary to reduce its production costs (since R. viscosum is strictly aerobic, the biopolymer should be produced ex situ and subsequently injected into the oil well). This can be achieved through the use of agro-industrial wastes or by-products as substrates for its production and through the optimization of the fermentation process, as reported for other biopolymers [25,26,38]. The temperature at which the viscosity of the (bio)polymer solution and the crude oil were measured in each study is indicated, as well as the temperature at which the oil recovery assay was performed.…”

A Strategy for Scleroglucan Production in Sclerotium Rolfsii: Lowering pH in Fermentation Process by Manipulating Oxalate Metabolic Pathway With CRISPR/Cas9 Tool

“…For example, pullulan from Aureobasidium pullulans, xanthan from Xanthomonas sp., hyaluronic acid from Streptococcus zooepidemicus, scleroglucan from Sclerotium rolfsii (Teleomorph: Athelia rolfsii) have been reported [4][5][6]. Because of unique structure and high molecular weight, scleroglucan has many properties so that it could be applied in oil recovery [7], food industry [8] and the pharmaceutical industry [9]. Scleroglucan is produced mainly via microbial fermentation.…”

Characterization of Microbial Communities Associated with Ceramic Raw Materials as Potential Contributors for the Improvement of Ceramic Rheological Properties

“…Because of their physical and rheological properties, these polymers confer potentially interesting applications to the industrial sector [3,4]. Many EPS, such as xanthan, alginate, dextran, pullulan and glucan, have a wide range of applications in food, pharmaceutical, biomedical, petroleum, and other industries [5][6][7]. Some properties of EPS should be considered of high interest for the technical ceramics industry to improve the rheological properties of the slips and to decrease the difficulties observed during the unidirectional dry pressing process.…”