One-step production of functional branched oligoglucosides with coupled fermentation of Pichia pastoris GS115 and Sclerotium rolfsii WSH-G01

A novel coupled fermentation system for low-molecular-weight xanthan gum with diverse biological activities

Xanthan gum (XG) is a bacterial exopolysaccharide widely used in various industries due to its stability and rheological properties. Low-molecular-weight xanthan gum (LXG) exhibits enhanced properties and broader applications, but current degradation methods are limited. This study introduces an innovative coupled fermentation system for the efficient production of LXG. Endo-xanthanase from Microbacterium sp. XT11 was expressed in Pichia pastoris GS115, exhibiting optimal activity at pH 6.0 and 40 °C, with broad pH tolerance. The optimized coupled fermentation system used bean sprouts juice as nitrogen source, the inoculation quantity of X. campestris: P. pastoris was 1: 3, and the pH was controlled at 6.0. In the bioreactor, the total sugar concentration reached 12.12 g/L, the reducing sugar concentration reached 5.32 g/L, and the endo-xanthanase activity increased to 1150.26 U/L, which were 2.13, 2.3, and 3.71 times higher than those at the shake flask level, respectively. The prepared LXG had a molecular weight of 1093 Da and a monosaccharide ratio of 2.0:1.57:0.89 (glucose, mannose, and glucuronic acid). Bioactivity analysis revealed its antioxidant and prebiotic properties, promoting the growth of beneficial intestinal microbiota and metabolite production. This suggests the potential of LXG as a functional ingredient in intestinal health-focused foods and supplements.

Advances in molecular enzymology of β-1,3-glucanases: A comprehensive review

β-1,3-Glucanases are essential enzymes involved in the hydrolysis of β-1,3-glucans, with significant biological and industrial relevance. These enzymes are derived from diverse sources, including bacteria, fungi, plants, and animals, each exhibiting unique substrate specificities and biochemical properties. This review provides an in-depth analysis of the natural sources and ecological roles of β-1,3-glucanases, exploring their enzymatic properties such as optimal pH, temperature, molecular weight, isoelectric points, and kinetic parameters, which are crucial for understanding their functionality and stability. Advances in molecular enzymology are discussed, focusing on gene cloning, expression in systems like Escherichia coli and Pichia pastoris, and structural-functional relationships. The reaction mechanisms and the role of non-catalytic carbohydrate-binding modules in enhancing substrate hydrolysis are examined. Industrial applications of β-1,3-glucanases are highlighted, including the production of β-1,3-glucooligosaccharides, uses in the food industry, biological control of plant pathogens, and nutritional roles. This review aims to provide a foundation for future research, improving the efficiency and robustness of β-1,3-glucanases for various industrial applications.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2021-2022

The use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry for the analysis of carbohydrates and glycoconjugates is a well-established technique and this review is the 12th update of the original article published in 1999 and brings coverage of the literature to the end of 2022. As with previous review, this review also includes a few papers that describe methods appropriate to analysis by MALDI, such as sample preparation, even though the ionization method is not MALDI. The review follows the same format as previous reviews. It is divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of computer software for structural identification. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other general areas such as medicine, industrial processes, natural products and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. MALDI is still an ideal technique for carbohydrate analysis, particularly in its ability to produce single ions from each analyte and advancements in the technique and range of applications show little sign of diminishing.

Optimized scleroglucan production by Athelia rolfsii and in vitro Sclg-5-fluorouracil release investigations

Scleroglucan is a notable member of the β-glucan microbial polysaccharides with a long tradition of industrial and therapeutic use. The local strain, previously identified as Athelia rolfsii TEMG MH 236106 produced an appreciable amount of scleroglucan using glucose as a carbon source and yeast extract as a nitrogen source. Plackett-Burman design was employed to effectively screen critical medium composition, culture, and fermentation conditions. Athelia rolfsii TEMG MH 236106 produced the maximum amount of scleroglucan (18.12 g/L) with a 45.3 % glucose conversion. Out of the eleven variables, the most effective factors showing a high level of significance are as follows: glucose, yeast extract, citric acid, inoculum disc numbers, culture volume and incubation time. An update to maximize scleroglucan production in the central composite design for four parameters (glucose and yeast extract concentrations, disc number, medium volume and incubation time) with 31 runs was applied and the production of scleroglucan reached its maximum at 31.56 g/L with 78.9 % glucose conversion. Three models of Sclg-5-fluorouracil complexes have been employed to study in vitro drug release investigations. Hence, the Sclg-5-FU (5 and 10 mg/mL) models appeared to be the most suitable for drug administration due to their concentration and distribution within capsules.

High-level secretory production of leghemoglobin in Pichia pastoris through enhanced globin expression and heme biosynthesis

Soy leghemoglobin is a key food additive that imparts meaty flavor and color to meat analogs. Here, a Pichia pastoris strain capable of high-yield secretory production of functional leghemoglobin was developed through gene dosage optimization and heme pathway consolidation. First, multi-copy integration of LegH expression cassette was achieved via both post-transformational vector amplification and CRISPR/Cas9 mediated genome editing methods. A combination of inducible expression and constitutive expression resulted in the highest production of leghemoglobin. Then, heme biosynthetic pathway was engineered to address challenges in heme depletion and leghemoglobin secretion. Finally, the disruption of ku70 was complemented in engineered P. pastoris strain to enable high-density fermentation in a 10-L bioreactor. These engineering strategies increased the secretion of leghemoglobin by more than 83-fold, whose maximal leghemoglobin titer and heme binding ratio reached as high as 3.5 g/L and 93 %, respectively. This represents the highest secretory production of heme-containing proteins ever reported.

One-pot fermentation for erythritol production from distillers grains by the co-cultivation of Yarrowia lipolytica and Trichoderma reesei

A co-fermentation process involving Yarrowia lipolytica and Trichoderma reesei was studied, using distillers grains (DGS) as feedstocks for erythritol production. DGS can be effectively hydrolyzed by cellulase in the single-strain culture of T. reesei. One-pot solid state fermentation for erythritol production was then established by co-cultivating Y. lipolytica M53-S with the 12 h delay inoculated T. reesei Rut C-30, in which efficient saccharification of DGS and improved production of erythritol were simultaneously achieved. The 10:1 inoculation proportion of Y. lipolytica and T. reesei contributed to the maximum erythritol production of 267.1 mg/gds under the optimal conditions including initial moisture of 55%, pH of 5.0, NaCl addition of 0.02 g/gds and DGS mass of 200 g in 144 h co-cultivation. Being compared with the attempts to produce erythritol from other raw materials, the one-pot SSF with DGS is proposed to be a potential strategy for efficient and economical erythritol production.

Efficient precious metal Rh(III) adsorption by waste P. pastoris and P. pastoris surface display from high-density culture

Rhodium is one of the most used precious metals in catalysis both in laboratory reactions and industrial processes. However, the adsorption of Rh(III) by microorganisms has been seldomly reported. In this work, waste P. pastoris and recombinant P. pastoris with surface-displayed Rh metal peptides (P. pastoris GS-R) from high-density culture were used as novel adsorbents to study Rh(III) adsorption. Under the optimal adsorption conditions of biomass of 0.25 g L^-1, pH of 1.2, temperature of 30 °C, and adsorption time of 2 h in simulated wastewater, the maximum adsorption ratios of 55.69% (110.1 mg g^-1) and 75.03% (142.11 mg g^-1) were achieved for waste P. pastoris and P. pastoris GS-R, respectively. Using the two adsorbents, the adsorption kinetic models fit the quasi-second-order equation, and isotherm models followed the Langmuir and Temkin equations, respectively. P. pastoris GS-R showed high adsorption capacity (48.49%) and selectivity (65.86%) in electroplating wastewater, and the desorption ratio reached 34.49% after treatment with 2 M HNO₃ and ultrasonic wave. Therefore, an environmental-friendly strategy was developed for the recovery of Rh(III) and other precious metals by using P. pastoris.

Production of prebiotic gellan oligosaccharides based on the irradiation treatment and acid hydrolysis of gellan gum

Biologically active gellan oligosaccharides (GOSs), newly found plant elicitors and biostimulants, are produced from the hydrolysis of gellan gum. Traditional hydrolysis with concentrated acid suffers from the problems of high pollution and low functional oligosaccharide yield because the process is difficult to control. Irradiation (⁶⁰Co γ-ray) with a dosage ranging from 0 kGy to 175 kGy was used to degrade gellan gum efficiently and cleanly into low molecular weight (M_w) gellan with an average M_w ranging from 449,119 Da to 72,903 Da. The low M_w gellan irradiated at 70 kGy was further hydrolyzed with low concentration acid (0.5 mol/L HCl) to produce GOSs with DPs mainly 4 and 8, indicating that the Rha-β-(1 → 3)-Glc bonds in gellan gum were easily cut to produce residues with tetrasaccharide repeat subunits. Besides antioxidant activity, GOSs were also proved with prebiotic activity by in vitro fecal fermentation in a self-designed bionic intestinal reactor.

Efficient Production of Scleroglucan by Sclerotium rolfsii and Insights Into Molecular Weight Modification by High-Pressure Homogenization

Scleroglucan is a non-ionic water-soluble polysaccharide, and has been widely used in the petroleum, food, medicine and cosmetics industries. Currently, scleroglucan is mainly produced by Sclerotium rolfsii. A higher level of scleroglucan (42.0 g/L) was previously obtained with S. rolfsii WSH-G01. However, the production of scleroglucan was reduced despite a higher glucose concentration remaining. Additionally, the molecular weight of scleroglucan was large, thus restricted its application. In this study, by adjusting the state of seeds inoculated, the degradation issue of scleroglucan during the fermentation process was solved. By comparing different fed-batch strategies, 66.6 g/L of scleroglucan was harvested by a two-dose fed-batch mode, with 53.3% glucose conversion ratio. To modify the molecular weight of scleroglucan, a combination method with HCl and high-pressure homogenization treatment was established. Finally, scleroglucan with molecular weight of 4.61 × 10⁵ Da was obtained. The developed approaches provide references for the biosynthesis and molecular weight modification of polysaccharides.