Conversion Of Polysaccharides Research Articles

Characterization of Degraded Konjac Glucomannan from an Isolated Bacillus licheniformis Strain with Multi-Enzyme Synergetic Action.

The large molecular weight and high viscosity of natural konjac glucomannan (KGM) limit its industrial application. Microbial degradation of low-molecular-weight KGM has health benefits and various biological functions; however, the available KGM strains used in the industry have microbial contamination and low degradation efficiencies. Therefore, exploring novelly adaptable strains is critical for industrial processes. Here, the Bacillus licheniformis Z7-1 strain isolated from decaying konjac showed high efficiency for KGM degradation. The monosaccharide composition of the degradation products had a reduced molar ratio of mannose to glucose, indicating that Z7-1 preferentially degraded glucose in KGM. The degraded component was further characterized by ESI-MS, Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), and it also exhibited good antibacterial activity against various food-spoilage bacteria. Genome sequencing and zymolytic analysis revealed that abundant carbohydrate-active enzymes exist in the Z7-1 genome, with at least five types of extracellular enzymes responsible for KGM degradation, manifesting multi-enzyme synergetic action. The extracellular enzymes had significant thermal stability, indicating their potential application in industry. This study provides an alternative method for obtaining low-molecular-weight KGM with antibacterial functions and supports foundational knowledge for its development as a biocatalyst for the direct conversion of biomass polysaccharides into functional components.

Development of sustainable sugarcane bagasse biorefinery using a greener deep eutectic solvent from hemicellulose-derived acids

Acid-based deep eutectic solvents (ADES) have recently been tested as an emerging technology in biomass deconstruction. In particular, the use of hemicellulose-derived carboxylic acids has attracted great interest as this type of ADES can enable a sustainable closed-loop biorefinery, due to their efficiency and recyclability. Therefore, this study proposed the pretreatment of sugarcane bagasse (SCB) with acetic acid, as a biomass-derived chemical, and choline chloride [ChCl]:AA to perform a complete biomass fractionation to enhance enzymatic digestibility. Thus, this work analyzed the effect of different temperatures and reaction time during pretreatment, studying the impact on biomass composition and digestibility during enzymatic hydrolysis. In addition, the reuse of ADES to produce an environmentally friendly and low-cost SCB biorefinery was explored by studying the physicochemical modifications in polysaccharide-rich material (PRM) and lignin-rich material (LRM) by ATR-FTIR and SEM photography. Furthermore, the ADES content was also characterized by HPLC after each recycling cycle. The results demonstrated efficient polysaccharide conversion, promoting an enrichment in glucan (>60%) and xylan (>20%) content under mild operating conditions (130°C and 90 min) supported by ATR-FTIR and SEM. Furthermore, SCB pretreated under these selected conditions achieved higher digestibility, increasing by 89% for glucan and 73% for xylan, using a simple and competitive process. In contrast, increasing the temperature above 130°C did not improve the enzymatic digestibility of SCB. Thus, ChCl:AA could be recycled and reused. Therefore, this study demonstrated the potential of AA in DES pretreatments as an environmentally friendly and efficient method for the valorization of SCB components.

Bisphenol A affects microbial interactions and metabolic responses in sludge anaerobic digestion.

The widespread use of bisphenol A (BPA) has resulted in the emergence of new pollutants in various environments, particularly concentrated in sewage sludge. This study investigated the effects of BPA on sludge anaerobic digestion, focusing specifically on the interaction of microbial communities and their metabolic responses. While the influence of BPA on methane accumulation is not significant, BPA still enhanced the conversion of soluble COD, protein, and polysaccharides. BPA also positively influenced the hydrolysis-acidogenesis process, leading to 17% higher concentrations of volatile fatty acids (VFAs). Lower BPA levels (0.2-0.5mg/kg dw) led to decreased hydrolysis and acidogenesis gene abundance, indicating metabolic inhibition; conversely, higher concentrations (1-5mg/kg dw) increased gene abundance, signifying metabolic enhancement. Diverse methane metabolism was observed and exhibited alterations under BPA exposure. The presence of BPA impacted both the diversity and composition of microbial populations. Bacteroidetes, Proteobacteria, Firmicutes, and Chloroflexi dominated in BPA-treated groups and varied in abundance among different treatments. Changes of specific genera Sedimentibacter, Fervikobacterium, Blvii28, and Coprothermobacter in response to BPA, affecting hydrolysis and acetogenesis. Archaeal diversity declined while the hydrogenotrophic methanogen Methanospirillum thrived under BPA exposure. BPA exposure enabled microorganisms to form structured community interaction networks and boost their metabolic activities during anaerobic digestion. The study also observed the enrichment of BPA biodegradation pathways at high BPA concentrations, which could interact and overlap to ensure efficient BPA degradation. The study provides insights into the digestion performance and interactions of microbial communities to BPA stress and sheds light on the potential effect of BPA during anaerobic digestion.

An Overview of Heterogeneous Catalysts Based on Hypercrosslinked Polystyrene for the Synthesis and Transformation of Platform Chemicals Derived from Biomass.

Platform chemicals, also known as chemical building blocks, are substances that serve as starting materials for the synthesis of various value-added products, which find a wide range of applications. These chemicals are the key ingredients for many fine and specialty chemicals. Most of the transformations of platform chemicals are catalytic processes, which should meet the requirements of sustainable chemistry: to be not toxic for humans, to be safe for the environment, and to allow multiple reuses of catalytic materials. This paper presents an overview of a new class of heterogeneous catalysts based on nanoparticles of catalytically active metals stabilized by a polymer matrix of hypercrosslinked polystyrene (HPS). This polymeric support is characterized by hierarchical porosity (including meso- and macropores along with micropores), which is important both for the formation of metal nanoparticles and for efficient mass transfer of reactants. The influence of key parameters such as the morphology of nanoparticles (bimetallic versus monometallic) and the presence of functional groups in the polymer matrix on the catalytic properties is considered. Emphasis is placed on the use of this class of heterogeneous catalysts for the conversion of plant polysaccharides into polyols (sorbitol, mannitol, and glycols), hydrogenation of levulinic acid, furfural, oxidation of disaccharides, and some other reactions that might be useful for large-scale industrial processes that aim to be sustainable. Some challenges related to the use of HPS-based catalysts are addressed and multiple perspectives are discussed.

Eat your beets: Conversion of polysaccharides into oligosaccharides for enhanced bioactivity

Bioactive oligosaccharides with the potential to improve human health, especially in modulating gut microbiota via prebiotic activity, are available from few natural sources. This work uses polysaccharide oxidative cleavage to generate oligosaccharides from beet pulp, an agroindustry by-product. A scalable membrane filtration approach was applied to purify the oligosaccharides for subsequent in vitro functional testing. The combined use of nano-LC/Chip Q-TOF MS and UHPLC/QqQ MS allowed the evaluation of the oligosaccharide profile and their monosaccharide complexity. A final product containing roughly 40 g of oligosaccharide was obtained from 475 g of carbohydrates. Microbiological bioactivity assays indicated that the product obtained herein stimulated desirable commensal gut bacteria. This rapid, reproducible, and scalable method represents a breakthrough in the food industry for generating potential prebiotic ingredients from common plant by-products at scale. Industrial relevanceThis work proposes an innovative technology based on polysaccharide oxidative cleavage and multi-stage membrane purification to produce potential prebiotic oligosaccharides from renewable sources. It also provides critical information to evidence the prebiotic potential of the newly generated oligosaccharides on the growth promotion ability of representative probiotic strains of bifidobacteria and lactobacilli.

Sustainable structural polysaccharides conversion: How does DES pretreatment affect cellulase adsorption, thereby improving enzymatic digestion of lignocellulose?

Biomass conversion aims at degrading the structural polysaccharides of lignocellulose into reducing sugars. Pretreatment is necessary to overcome the recalcitrance of lignocellulose. The DES La/ChCl in this paper was selected based on our previous study. To examine cellulase adsorption of lignocellulose after DES pretreatment, sorghum straw was pretreated with DES under different condition. The adsorption improvement of cellulase on lignocellulose after DES pretreatment has positive impact on reducing sugar production of biomass. After DES pretreatment, 1. pore corrosion caused the upward trend of pore radius and the downward trend of SSA. 2. the hydrogen bounding force of pretreated sorghum straw and MCC decreased, the hydrogen bounding force of pretreated lignin increased. 3. although the unsaturation of pretreated lignin increased, DES pretreatment is helpful for the removal of lignin. 4. The decrease in the hydrophobicity of sorghum straw make it easier to disperse. 5. the Zeta potential of pretreated sorghum straw shifted towards the positively charged region, while pretreated lignin shifted towards the negatively charged region. 6. different adsorption behaviors were observed in specific components of cellulase mixtures (BGs, CBHs, EGs and xlylanase). These results revealing the mechanism of enzyme adsorption are conductive for understanding the role of pretreatment in biomass conversion.

Enhanced biomass processing towards acetone-butanol-ethanol fermentation using a ternary deep eutectic solvent

This work evaluated the effectiveness of ternary deep eutectic solvents (DES) composed of cholinium chloride (ChCl), lactic acid (LA) and a diol (ethylene glycol – EG, or 1,6-hexanediol – HEX) in the pretreatment of rice straw (RS) towards the production of biobutanol. The most promising results were obtained with ChCl:LA:EG 1:5:5 at 120 °C for 4 h, which enabled the highest conversion of biomass polysaccharides into glucose and xylose up to 89.3 % and 53.6 % yields, respectively. Subsequently, the produced sugars were efficiently converted into biobutanol through the acetone-butanol-ethanol (ABE) fermentation process, resulting in the production of 95.7 g butanol/kg RS as one of the highest values reported in literature. Thus, the application of the ternary DES ChCl:LA:EG 1:5:5 represents a competitive and environmentally friendly pathway for RS valorization in comparison to conventional processes.

Fermentation-mediated variations in structure and biological activity of polysaccharides from Tetrastigma hemsleyanum Diels et Gilg

Variations in the structure and activities of polysaccharides from Tetrastigma hemsleyanum Diels et Gilg fermented by Sanghuangporus sanghuang fungi were investigated. Compare with the unfermented polysaccharide (THDP2), the major monosaccharide composition and molecular weight of polysaccharide after fermentation (F-THDP2) altered dramatically, which caused galactose-induced conversion from glucose and one-third of molecular weight. F-THDP2 had a molecular weight of 1.23 × 104 Da. Moreover, the glycosidic linkage of F-THDP2 varied significantly, a 1, 2-linked α-d-Galp and 1, 2-linked α-d-Manp backbone was established in F-THDP2, which differed from that of 1, 4-linked α-d-Glcp and 1, 4-linked β-d-Galp in THDP2. In addition, F-THDP2 showed a more flexible chain conformation than that of THDP2 in aqueous solution. Strikingly, F-THDP2 exhibited superior inhibitory effects on HeLa cells via Fas/FasL-mediated Caspase-3 signaling pathways than that of the original polysaccharide. These variations in both structure and biological activities indicated that fermentation-mediated modification by Sanghuangporus sanghuang might a promising novel method for the effective conversion of starch and other polysaccharides from Tetrastigma hemsleyanum Diels et Gilg into highly bioactive biomacromolecules, which could be developed as a potential technology for use in the food industry.

Highly efficient production of polyhydroxybutyrate using an open dual one-pot fermentation by Halomonas alkalicola M2

The high cost associated with polyhydroxybutyrate (PHB) production demands immediate attention to advance its commercial viability. Herein, we innovatively construct highly efficient production of PHB from low-cost lignocellulosic biomass (LCB) using an open one-pot fermentation by the alkali-halophilic Halomonas alkalicola M2 developed in our previous work. We first develop alkaline pretreatment of LCB to achieve open one-pot fermentation and efficient conversion. Multi-objective optimization of fermentation conditions produces 103.421 mg/L of PHB with a content of 14.437 % and effectively promotes saccharification with cellulose and xylan enzymatic efficiencies of 82.948 % and 73.710 %, respectively. We then develop an open dual one-pot fermentation process, involving the conversion of lignin- and lignin-derived compounds-enriched slurry in the first pot and subsequent polysaccharide conversion in the second pot, to achieve efficient whole LCB components conversion, yielding a record 9.57 g/L of PHB. More importantly, we extend an open dual one-pot-fed-batch fermentation, producing 0.80 g/L of PHB with 27.69 % content in the first pot and 20.08 g/L of PHB with 61.86 % content in the second pot, showing significantly higher than many reported strains. Overall, this work demonstrates the effectiveness of utilizing cheap LCB in a newly designed fermentation process to produce PHB efficiently, representing a significant advancement in this field.

Improving the Cellulose Enzymatic Digestibility of Sugarcane Bagasse by Atmospheric Acetic Acid Pretreatment and Peracetic Acid Post-Treatment.

Pretreatment of sugarcane bagasse (SCB) by aqueous acetic acid (AA), with the addition of sulfuric acid (SA) as a catalyst under mild condition (<110 °C), was investigated. A response surface methodology (central composite design) was employed to study the effects of temperature, AA concentration, time, and SA concentration, as well as their interactive effects, on several response variables. Kinetic modeling was further investigated for AA pretreatment using both Saeman's model and the Potential Degree of Reaction (PDR) model. It was found that Saeman's model showed a great deviation from the experimental results, while the PDR model fitted the experimental data very well, with determination coefficients of 0.95-0.99. However, poor enzymatic digestibility of the AA-pretreated substrates was observed, mainly due to the relatively low degree of delignification and acetylation of cellulose. Post-treatment of the pretreated cellulosic solid well improved the cellulose digestibly by further selectively removing 50-60% of the residual linin and acetyl group. The enzymatic polysaccharide conversion increased from <30% for AA-pretreatment to about 70% for PAA post-treatment.

Hierarchical zeolite with open tin sites stabilized by metal ions catalyze the conversion of polysaccharides to alkyl lactates

The high yield of alkyl lactate from polysaccharides is attractive and challenging. Here, we report the remarkable catalytic ability of hierarchical tin-containing Beta zeolites for this process. The hierarchical structure, mediated by polystyrene microspheres or starch, improves mass transfer in the polysaccharide conversion. Two types of acidic sites in the zeolite achieved cooperation in the cascade conversion. Brønsted acid associated with Al promoted the hydrolysis of polysaccharides to monosaccharides; the abundant open Sn site stabilized by Ni2+ converted the monosaccharides to alkyl lactate. Polydextrose was used as a substrate in various alcohols, yielding up to 44% for methyl lactate, 37% for ethyl lactate, and 36% for propyl lactate, and the catalytic yields were consistent throughout three runs. More than 90% of the catalytic capability was recovered by the ion exchange and calcination procedures.

Lytic polysaccharide monooxygenases: enzymes for controlled and site-specific Fenton-like chemistry.

The discovery of oxidative cleavage of glycosidic bonds by enzymes currently known as lytic polysaccharide monooxygenases (LPMOs) has profoundly changed our current understanding of enzymatic processes underlying the conversion of polysaccharides in the biosphere. LPMOs are truly unique enzymes, harboring a single copper atom in a solvent-exposed active site, allowing them to oxidize C-H bonds at the C1 and/or C4 carbon of glycosidic linkages found in recalcitrant, often crystalline polysaccharides such as cellulose and chitin. To catalyze this challenging reaction, LPMOs harness and control a powerful oxidative reaction that involves Fenton-like chemistry. In this essay, we first draw a brief portrait of the LPMO field, notably explaining the shift from the monooxygenase paradigm (i.e., using O2 as cosubstrate) to that of a peroxygenase (i.e., using H2O2). Then, we briefly review current understanding of how LPMOs generate and control a hydroxyl radical (HO•) generated through Cu(I)-catalyzed H2O2 homolysis, and how this radical is used to create the proposed Cu(II)-oxyl species, abstracting hydrogen atom of the C-H bond. We also point at the complexity of analyzing redox reactions involving reactive oxygen species and address potential deficiencies in the interpretation of existing LPMO data. Being the first copper enzymes shown to enable site-specific Fenton-like chemistry, and maybe not the only ones, LPMOs may serve as a blueprint for future research on monocopper peroxygenases.

Biomass derived bifunctional catalyst for the conversion of cassava dreg into sorbitol

A biomass derived bifunctional catalyst (Ru/CCD-SO3H) was used for one-pot conversion of cassava dreg and cassava starch into sorbitol. The cassava dreg is mainly composed of residual cassava starch and holocellulose. The highest sorbitol yield of 11.43 % was achieved using cassava dreg as reactant. A synergistic catalytic effect of acid and metal sites of Ru/CCD-SO3H on cassava starch conversion to sorbitol was observed. The maximum sorbitol yield reached 82.51 % using cassava starch as reactant. A kinetic model of cassava starch degradation was performed. The reaction rate constants of cassava starch degradation, glucose conversion and sorbitol generation improved with enhancing temperature. The activation energy of cassava starch hydrolysis is larger than that of glucose hydrogenation, indicating the cassava starch hydrolysis is rate-determining step of cassava starch conversion into sorbitol. This work not only realizes the comprehensive utilization of cassava dreg, but also provides useful guidance for developing kinetic model of polysaccharide conversion.

Optimisation of alkaline pretreatment of spent coffee grounds for microbial oil production by Cryptococcus curvatus

In a world of finite resources, the transition to a sustainable post-fossil resources economy is essential. Within this concept, spent coffee grounds (SCGs) could be used for the production of bio-based chemicals, biopolymers and value-added products. Lipids and phenolics were initially extracted from SCGs. Alkaline pretreatment of the remaining SCGs solids has been optimised in this study via Central Composite Design to maximise lignin removal and overall sugar to polysaccharide conversion yield. The optimal SCGs pretreatment conditions were 0.06% (w/v) NaOH and 99.5 °C resulting in 35.7% lignin removal at 60 min pretreatment duration with low glucan and hemicellulose losses (ca. 2.5%). Enzymatic hydrolysis of the remaining SCGs alkaline pretreated solids resulted in 79.4% glucan, 74.5% mannan and 54.8% hemicellulose hydrolysis yield. The SCGs hydrolysate was used as fermentation feedstock in bioreactor cultures of Cryptococcus curvatus resulting in 36.1 g/L microbial oil with 0.25 g/g yield and 0.41 g/(L∙h) productivity. The total dry weight reached 62.7 g/L corresponding to 57.5% (w/w) intracellular lipid content. The microbial oil was rich in oleic acid (55.6%) followed by palmitic acid (18.9%) and stearic acid (14.0%). The proposed process led to the production of 7.81 g microbial oil per 100 g antioxidant- and oil-free SCGs.

One Step Catalytic Conversion of Polysaccharides in Ulva prolifera to Lactic Acid and Value-Added Chemicals

The production of lactic acid and value-added chemicals (such as hydroxypropanone, glycolic acid, and formic acid) directly from Ulva prolifera via one-step catalytic process was studied. The effect of different amounts of YCl3-derived catalysts on the hydrothermal conversion of carbohydrates in Ulva prolifera was explored, and the reaction conditions were optimized. In this catalytic system, rhamnose could be extracted from Ulva prolifera and converted in situ into lactic acid and hydroxypropanone at 160 °C, while all the glucose, xylose, and rhamnose were fractionated and completely converted to lactic acid at 220 °C or at a higher temperature, via several consecutive and/or parallel catalytic processes. The highest yield of lactic acid obtained was 31.4 wt% under the optimized conditions. The hydrothermal conversion of Ulva prolifera occurred rapidly (within 10 min) and showed promise to valorize Ulva prolifera.

Production of Biomodified Bleached Kraft Pulp by Catalytic Conversion Using Penicillium verruculosum Enzymes: Composition, Properties, Structure, and Application

The global development of the bioeconomy is impossible without technologies for comprehensive processing of plant renewable resources. The use of proven pretreatment technologies raises the possibility of the industrial implementation of the enzymatic conversion of polysaccharides from lignocellulose considering the process’s complexity. For instance, a well-tuned kraft pulping produces a substrate easily degraded by cellulases and hemicelulases. Enzymatic hydrolysis of bleached hardwood kraft pulp was carried out using an enzyme complex of endoglucanases, cellobiohydrolases, β-glucosidases, and xylanases produced by recombinant strains of Penicillium verruculosum at a 10 FPU/g mixture rate and a 10% substrate concentration. As a result of biocatalysis, the following products were obtained: sugar solution, mainly glucose, xylobiose, xylose, as well as other minor reducing sugars; a modified complex based on cellulose and xylan. The composition of the biomodified kraft pulp was determined by HPLC. The method for determining the crystallinity on an X-ray diffractometer was used to characterize the properties. The article shows the possibility of producing biomodified cellulose cryogels by amorphization with concentrated 85% H3PO4 followed by precipitation with water and supercritical drying. The analysis of the enzymatic hydrolysate composition revealed the predominance of glucose (55–67%) among the reducing sugars with a maximum content in the solution up to 6% after 72 h. The properties and structure of the modified kraft pulp were shown to change during biocatalysis; in particular, the crystallinity increased by 5% after 3 h of enzymatic hydrolysis. We obtained cryogels based on the initial and biomodified kraft pulp with conversion rates of 35, 50, and 70%. The properties of these cryogels are not inferior to those of cryogels based on industrial microcrystalline cellulose, as confirmed by the specific surface area, degree of swelling, porosity, and SEM images. Thus, kraft pulp enzymatic hydrolysis offers prospects not only for producing sugar-rich hydrolysates for microbiological synthesis, but also cellulose powders and cryogels with specified properties.

Peroxide-mediated selective conversion of biomass polysaccharides over high entropy sulfides via solar energy catalysis

Biomass polysaccharides are converted over novel high-entropy sulfides (CdZnCuCoFe)Sx under mild reaction conditions via solar energy catalysis. A large amount of carbon monoxide (CO) was produced at 1.73 mmol g−1 h−1 with a high selectivity of 99.1% among the gas products.

Compositional Analysis and identification of bio-oil in Iraqi Date Pits

Iraq is known with the abundance of date palm trees. This can be an important source of food nutrients and agricultural waste for energy. Date pits represent 18-20% of the fruit weight, and are recognized for their oil content and other nutritional components. This agricultural waste can be of great importance as a source of biofuel or useful nutritional compounds. In this paper, date pits of the most common variety of dates in Iraq named Zahdi, was investigated for compositional analysis and biomass value assessment. Samples of dried pits were examined for sugars, wax &amp; chlorophyll and total inorganic ash content. In addition, structural sugars were examined to assess the potential of producing biofuel from date pits. It is found that the total content of structural sugars was 62.16% mainly Arabinose (53.56%). This highly significant percentage of Arabinose in date pits has not been reported in literature till the present. Further analysis of the volatile organic compounds in the pits via pyrolysis, identified a rare sugar in nature named D-allose. It is believed that thermochemical conversion of polysaccharides has led to produce the monosaccharide d-allose sugar. It is the first time ever to identify this rare sugar in Iraqi date pits with a noticeable amount. The importance of this finding comes from the recent medical investigations that proved the inhibiting activity of D-allose on many carcinoma cells in the human body.

Hydrolytic Oxidation of Cellobiose Using Catalysts Containing Noble Metals

Studies of the processes of the hydrolytic oxidation of disaccharides are the first step towards the development of technologies for the direct conversion of plant polysaccharides, primarily cellulose, into aldonic and aldaric acids, which are widely used in chemical synthesis and various industries. In this study, heterogeneous catalysts based on a porous matrix of hypercrosslinked polystyrene (HPS) and noble metals (Pt, Au, Ru, and Pd) were proposed for the hydrolytic oxidation of cellobiose to gluconic and glucaric acids. The catalysts were characterized using low-temperature nitrogen adsorption, hydrogen chemisorption, electron microscopy, and other methods. In particular, it was shown that the Pt-containing catalyst contained, on average, six times more active centers on the surface, which made it more promising for use in this reaction. At a temperature of 145 °C, an O2 pressure of 5 bars, and a substrate/catalyst weight ratio of 4/1, the yields of gluconic and glucaric acids reached 21.6 and 63.4%, respectively. Based on the data obtained, the mathematical model of the cellobiose hydrolytic oxidation kinetics in the presence of 3% Pt/HPS MN270 was developed, and the parameter estimation was carried out. The formal description of the kinetics of cellobiose hydrolytic oxidation was obtained.

Insights into promiscuous chitosanases: the known and the unknown.

Chitosanase, a glycoside hydrolase (GH), catalyzes the cleavage of β-1,4-glycosidic bonds in polysaccharides and is widely distributed in nature. Many organisms produce chitosanases, and numerous chitosanases in the GH families have been intensely studied. The reported chitosanases mainly cleaved the inter-glucosamine glycosidic bonds, while substrate specificity is not strictly unique due to the existence of bifunctional or multifunctional activity profiles. The promiscuity of chitosanases is essential for the different pathways of biomass polysaccharide conversion and understanding of the chitosanase evolutionary process. However, the reviews for this aspect are completely unknown. This review provides an overview of the promiscuous activities, also considering the substrate and product specificity of chitosanases observed to date. These contribute to important implications for the future discovery and research of promiscuous chitosanases and applications related to biomass conversion. KEY POINTS: • The promiscuity of chitosanases is reviewed for the first time. • The current review provides insights into the substrate specificity of chitosanases. • The mode-product relationship and prospect of promiscuous chitosanases are highlighted.