Inhibition and kinetic studies of cellulose- and hemicellulose-degrading enzymes of Ganoderma boninense by naturally occurring phenolic compounds

Understanding the characteristic changes of retrogradation behavior and edible quality of brown rice modified with inhibiting retrogradation enzymes of Ganoderma lucidum

Brown rice (BR) has gradually become a new choice for consumers due to its exceptionally nutritional value. Whereas starch retrogradation profoundly reduces its edibility, shelf-life and consumer acceptance, limiting the development of BR and even other starch-based food products. So, it is crucial for controlling the retrogradation properties of brown rice starch (BRS), and which has received significant attention in the food industry. Enzymatic modification is considered as an effective manner to retard starch retrogradation by degrading starch to an appropriate extent. Ganoderma lucidum can secrete various hydrolytic enzymes related to starch hydrolysis, providing a theoretical basis and feasibility for improving the starch retrogradation. Our study delves into characteristic changes of brown rice (BR) and its starch (BRS) when modified by the intracellular enzyme of Ganoderma lucidum, which contains several inhibiting retrogradation enzymes (GlIRE), mainly including α-amylase, β-amylase, and cellulase. GlIRE treatments significantly decreased the setback viscosity to 1544.33 ± 24.01 cP (2 h), diffraction intensities and relative crystallinity to 21.90 ± 0.06% (2 h) and 19.22 ± 0.19% (3 h) as per RVA and XRD analysis, accompanied with more pits and pores in surface morphology. The DSC analysis showed that GlIRE treatments significantly depressed the gelatinization enthalpy to 5.86 ± 0.46 J/g (2 h) and retrogradation enthalpy. FT-IR analysis also indicated the contribution of GlIRE treatments to retard starch retrogradation, including shifting the peaks of 3500 cm-1-3200 cm-1 to lower wave numbers and decreasing the transmittance, as well as R1047/R1022 values reducing from 0.87 to 0.73, mainly due to the shortening of starch chain length and the weakening of hydrogen bonding strength between or within the molecular chains. Simultaneously, it aslo found that GlIRE treatments effectively improved the textural properties of BR, with reducing of hardness, chewiness and gumminess, and increasing of adhesiveness. Interestingly, GC-MS analysis showed that GlIRE treatments could also significantly affect the types and contents of volatile compounds in BR. Our study highlights the efficacy of GlIRE in starch retrogradation and rice quality-improvement, showcasing a new expansion of the research and application of G. lucidum and a science-based strategy for developing the edible quality of starch-based food.

An In-Depth Study of Phytopathogenic Ganoderma: Pathogenicity, Advanced Detection Techniques, Control Strategies, and Sustainable Management

Phytopathogenic Ganoderma species pose a significant threat to global plant health, resulting in estimated annual economic losses exceeding USD (US Dollars) 68 billion in the agriculture and forestry sectors worldwide. To combat this pervasive menace effectively, a comprehensive understanding of the biology, ecology, and plant infection mechanisms of these pathogens is imperative. This comprehensive review critically examines various aspects of Ganoderma spp., including their intricate life cycle, their disease mechanisms, and the multifaceted environmental factors influencing their spread. Recent studies have quantified the economic impact of Ganoderma infections, revealing staggering yield losses ranging from 20% to 80% across various crops. In particular, oil palm plantations suffer devastating losses, with an estimated annual reduction in yield exceeding 50 million metric tons. Moreover, this review elucidates the dynamic interactions between Ganoderma and host plants, delineating the pathogen's colonization strategies and its elicitation of intricate plant defense responses. This comprehensive analysis underscores the imperative for adopting an integrated approach to Ganoderma disease management. By synergistically harnessing cultural practices, biological control, and chemical treatments and by deploying resistant plant varieties, substantial strides can be made in mitigating Ganoderma infestations. Furthermore, a collaborative effort involving scientists, breeders, and growers is paramount in the development and implementation of sustainable strategies against this pernicious plant pathogen. Through rigorous scientific inquiry and evidence-based practices, we can strive towards safeguarding global plant health and mitigating the dire economic consequences inflicted by Ganoderma infections.

Rational design and identification of novel thiosemicarbazide derivatives as laccase inhibitors

BACKGROUND

Laccase is a key enzyme in the fungal 1,8-dihydroxynaphthalene (DHN) melanin biosynthesis pathway, which is a potential target for the control of pathogenic fungi. In our previous work, compound a2 was found with higher inhibition activity against laccase and antifungal activity than laccase inhibitor PMDD-5Y. The introduction of hydrogen-bonded receptors in the amino part was found to be beneficial in improving laccase inhibitory activity by target-based-biological rational design. In this work, the hydrogen-bonded receptors morpholine and piperazine were introduced for structure optimization to enhancing biological activity.

RESULTS

Enzyme activity tests indicated that all target compounds had inhibitory activity against laccase, and some compounds exhibited better activity against laccase than a2, it was further verified that the introduction of hydrogen-bonded receptors in the amino portion could enhance the laccase inhibitory activity of target compounds. Most compounds showed excellent antifungal activities in vitro. Compound m14 displayed good activity against Magnaporthe oryzae both in vitro and in vivo. The scanning electron microscopy (SEM) analysis showed that the mycelium of M. oryzae treated with m14 were destroyed. Molecular docking revealed the binding mode between laccase and target compounds.

CONCLUSION

Thirty-eight compounds were synthesized and showed good inhibitory activity against laccase, the introduction of morpholine and piperazine in the amino part was beneficial to improve antifungal activity and laccase activity. Further validation of laccase as a potential target for rice blast control, while m14 can be used as a candidate compound for the control of rice blast. © 2023 Society of Chemical Industry.

In vitro Evaluation of Anti-Inflammatory Activity of "Habanero" Chili Pepper (Capsicum chinense) Seeds Extracts Pretreated with Cellulase

The aim of this study was to explore the effect of capsaicin and particular phenolic compounds profile from cellulase assisted extracts of Habanero (Capsicum chinense) chili pepper seeds (CPS) on the concentration of cytokines (IL-2, IL-6, TNF-α, IL-1β) in murine macrophages (RAW 264.7) stimulated with lipopolysaccharides (LPS). Capsaicin was quantified by HPLC-DAD, and the phenolic profile was determined by UPLC-MS-QqQ. Anti-inflammatory activity was evaluated by Mouse Cytokine/Chemokine Magnetic Bead Panel 96-well plate assay. Among the 15 different phenolics found in CPS extracts obtained at 120 or 150 min of maceration with 2,500 UI/L at 30 ºC or 45 ºC in a 1:15 (w:v) proportion, the most abundant was vanillic acid (7.97-12.66 µg/g). The extract obtained at 30 ºC and 120 min, showed similar effects than the observed for synthetic anti-inflammatory drugs indomethacin and dexamethasone, and capsaicin standard. Beyond capsaicin, salicylic, protocatechuic and trans-cinnamic acids as well as vanillin in CPS extracts were correlated with the anti-inflammatory effect. On the other hand, capsaicin and chlorogenic acid contents were potential immunostimulants whose concentration varied depending on the cellulase treatment time.

Towards efficient enzymatic saccharification of pretreated lignocellulose: Enzyme inhibition by lignin-derived phenolics and recent trends in mitigation strategies

Lignocellulosic biorefinery based on its sugar-platform has been considered as an efficient strategy to replace fossil fuel-based refinery. In the bioconversion process, pretreatment is an essential step to firstly open up lignocellulose cell wall structure and enhance the accessibility of carbohydrates to hydrolytic enzymes. However, various lignin and/or carbohydrates degradation products (e.g. phenolics, 5-hydroxymethylfurfural, furfural) also generated during pretreatment, which severely inhibit the following enzymatic hydrolysis and the downstream fermentation process. Among them, the lignin derived phenolics have been considered as the most inhibitory compounds and their inhibitory effects are highly dependent on the source of biomass and the type of pretreatment strategy. Although liquid-solid separation and subsequent washing can remove the lignin derived phenolics and other inhibitors, this is undesirable in the realistic industrial application where the whole slurry of pretreated biomass need to be directly used in the hydrolysis process. This review summarizes the phenolics formation mechanism for various commonly applied pretreatment methods and discusses the key factors that affect the inhibitory effect of phenolics on cellulose hydrolysis. In addition, the recent achievements on the rational design of inhibition mitigation strategies to boost cellulose hydrolysis for sugar-platform biorefinery are also introduced. This review also provides guidance for rational design detoxification strategies to facilitate whole slurry hydrolysis which helps to realize the industrialization of lignocellulose biorefinery.

Enzyme-assisted extraction of anti-inflammatory compounds from habanero chili pepper (Capsicum chinense) seeds

Capsaicinoids are the main bioactive compounds extracted from chili pepper seeds (CPSs) but other bioactive compounds such as phenolic compounds may be found. Enzyme-assisted extraction (EAE) improves the extraction of bioactive compounds from fruits and seeds. The aim of this study was to establish the cellulase-assisted extraction conditions of capsaicinoids and phenolic compounds from Habanero CPSs (Capsicum chinense) and to evaluate the anti-inflammatory activity of the obtained extracts on murine macrophages. EAE was performed using different temperatures (T1 = 30°C, T2 = 45°C and T3 = 60°C), enzyme concentrations (E1 = 2,500 UI/L and E2 = 250 UI/L), and extraction time periods (0-150 min). Total phenolic compounds were quantified using the Folin-Ciocalteu assay, capsaicin (CAP) and dihydrocapsaicin (DHC) contents were evaluated by HPLC, and anti-inflammatory activity was performed with Griess assay on murine macrophage RAW 264.7 cell culture. The highest phenolic compound content (337.96 mg GAE/L) was achieved at 30°C, 2,500 UI/L, and 150 min of extraction. The highest CAP content (310.23 μg/ml) was obtained at 45°C with 250 UI/L for 150 min, while for DHC (167.72 μg/ml), the conditions were 60°C, 2,500 UI/L, and 120 min. The highest anti-inflammatory response was obtained when 60°C, E2, and 150 min were used for the extraction, and nitric oxide (NO) production was reduced to 22.56%. Based on the results obtained in this research, EAE allowed the recovery of compounds with anti-inflammatory activity from CPS using water as a solvent. There was a correlation between the extraction of CAP and DHC. But although a moderate direct correlation between the concentration of capsaicinoids and total phenolic compounds (TPCs) and an inverse correlation of the presence of the bioactive compounds (TPC, CAP, and DHC) with the NO synthesis, these were not statistically significant. We demonstrated that Habanero seeds are an important raw material to recover anti-inflammatory compounds beyond capsaicinoids using water in EAE.

Solid-State Fermentation of Chestnut Shells and Effect of Explanatory Variables in Predictive Saccharification Models

In this study, chestnut shells (CNS), a recalcitrant and low-value agro-industrial waste obtained during the peeling of Castanea sativa fruits, were subjected to solid-state fermentation by six white-rot fungal strains (Irpex lacteus, Ganoderma resinaceum, Phlebia rufa, Bjerkandera adusta and two Trametes isolates). After being fermented, CNS was subjected to hydrolysis by a commercial enzymatic mix to evaluate the effect of fermentation in saccharification yield. After 48 h hydrolysis with 10 CMCase U mL−1 enzymatic mix, CNS fermented with both Trametes strains was recorded with higher saccharification yield (around 253 mg g−1 fermented CNS), representing 25% w/w increase in reducing sugars as compared to non-fermented controls. To clarify the relationships and general mechanisms of fungal fermentation and its impacts on substrate saccharification, the effects of some independent or explanatory variables in the production of reducing sugars were estimated by general predictive saccharification models. The variables considered were lignocellulolytic activities in fungal fermentation, CNS hydrolysis time, and concentration of enzymatic hydrolysis mix. Multiple linear regression analysis revealed a very high significant effect (p < 0.0001) of fungal laccase and xylanase activities in the saccharification models, thus proving the key potential of these enzymes in CNS solid-state fermentation.

Deciphering the Physicochemical and Microscopical Changes in Ganoderma boninense-Infected Oil Palm Woodblocks under the Influence of Phenolic Compounds

The threat of Ganoderma boninense, the causal agent of basal stem rot disease, in the oil palm industry warrants finding an effective control for it. The weakest link in the disease management strategy is the unattended stumps/debris in the plantations. Hence, this study aimed to determine whether the selected phenolic compounds could control G. boninense in inoculated oil palm woodblocks and restrict wood biodegradation. Results indicated a significant reduction in the wood mass loss when treated with all the phenolic compounds. Surprisingly, syringic and vanillic acids behaved ambivalently; at a lower concentration, the wood mass loss was increased, but it decreased as the concentrations were increased. In all four phenolic compounds, the inhibition of mass loss was dependent on the concentration of the compounds. After 120 days, the mass loss was only 31%, with 63% relative degradation of lignin and cellulose, and 74% of hemicellulose and wood anatomy, including silica bodies, were intact in those woodblocks treated with 1 mM benzoic acid. This study emphasizes the physicochemical and anatomical changes occurring in the oil palm wood during G. boninense colonization, and suggests that treating oil palm stumps with benzoic acid could be a solution to reducing the G. boninense inoculum pressure during replantation in a sustainable manner.

Current strategies and perspectives in detection and control of basal stem rot of oil palm

The rapid expansion of oil palm (OP) has led to its emergence as a commodity of strategic global importance. Palm oil is used extensively in food and as a precursor for biodiesel. The oil generates export earnings and bolsters the economy of many countries, particularly Indonesia and Malaysia. However, oil palms are prone to basal stem rot (BSR) caused by Ganoderma boninense which is the most threatening disease of OP. The current control measures for BSR management including cultural practices, mechanical and chemical treatment have not proved satisfactory. Alternative control measures to overcome the G. boninense problem are focused on the use of biological control agents and many potential bioagents were identified with little proven practical application. Planting OP varieties resistant to G. boninense could provide the ideal long-term solution to basal stem rot. The total resistance of palms to G. boninense has not yet been reported, and few examples of partial resistances have been observed. Importantly, basidiospores are now recognized as the method by which the disease is spread, and control methods require to be revaluated because of this phenomenon. Many methods developed to prevent the spread of the disease effectively are only tested at nursery levels and are only reported in national journals inhibiting the development of useful techniques globally. The initial procedures employed by the fungus to infect the OP require consideration in terms of the physiology of the growth of the fungus and its possible control. This review assesses critically the progress that has been made in BSR development and management in OP.

Pretreatment of Grape Stalks by Fungi: Effect on Bioactive Compounds, Fiber Composition, Saccharification Kinetics and Monosaccharides Ratio

Grape stalks, an inedible lignocellulosic residue from winemaking and agro-industrial grape juice production, can be valorized as a source of bioactive compounds and as feedstock for the saccharification and bioconversion of soluble sugars. Solid-state fermentation (SSF) by six white-rot fungi was applied as pretreatment. Fiber composition, free radical scavenging activity, four ligninolytic, and three hydrolytic enzyme activities were determined. Saccharification kinetics, yield, and productivity were evaluated and complemented with scanning electron microscopy (SEM), high performance liquid chromatography (HPLC) quantification of monosaccharides, and principal component analysis (PCA). After SSF, the biomass exhibited a drastic free radical scavenging activity decrease and the main enzymes produced were manganese-dependent peroxidase and xylanase. Scanning electron microscopy revealed the erosion of cell walls, and PCA exhibited a negative correlation between saccharification, and neutral detergent fiber and acid detergent lignin. Phlebia rufa pretreated biomass gave the highest sugars yield and productivity, representing a nearly three-fold increase compared to untreated samples. Also, monosaccharides quantification revealed that the 1:1 ratio of glucose to the sum of xylose plus galactose changes to the value of 2:1 after pretreatment. In this work, and for the first time, P. rufa proved to be an effective pretreatment of grape stalks for the saccharification and further bioconversion into value-added chemicals. In addition, lignocellulolytic enzymes were also produced through SSF.

Lignocellulosic pretreatment-mediated phenolic by-products generation and their effect on the inhibition of an endo-1,4-β-xylanase from Thermomyces lanuginosus VAPS-24

The inhibitory effect of eight model lignin derivatives (ferulic acid, guaiacol, kraft lignin (alkali, low sulfonate content), p-coumaric acid, gallic acid, syringic acid, vanillin and vanillic acid) on XynA activity was evaluated. The model lignin derivatives viz. gallic acid, vanillic acid and vanillin were inhibitory to XynA activity, with an over 50% reduction in activity at concentrations as low as 0.5 mg/ml. However, enzyme deactivation studies in the absence of substrate showed that these pretreatment by-products do not interact with the enzyme except when in the presence of its substrate. The effect of the main structural properties of the pretreatment-derived phenolics, for example their hydroxyl and carbonyl group types, on XynA enzyme inhibition was investigated. The presence of carbonyl groups in phenolics appeared to confer stronger inhibitory effects than hydroxyl groups on XynA activity. The hydrolytic potential of XynA was not inhibited by a mixture of phenolics derived after steam pretreatment of woody biomass (Douglas fir and Black wattle). It appears as if the liquors from steam-pretreated woody biomass did not possess high enough phenolic content to confer XynA inhibition. The xylanase (XynA from Thermomyces lanuginosus) is, therefore, a striking choice for application in biofuel and fine chemical industries for the xylan degradation in steam-pretreated biomass.

Insight into plant cell wall degradation and pathogenesis of Ganoderma boninense via comparative genome analysis

Background

G. boninense is a hemibiotrophic fungus that infects oil palms (Elaeis guineensis Jacq.) causing basal stem rot (BSR) disease and consequent massive economic losses to the oil palm industry. The pathogenicity of this white-rot fungus has been associated with cell wall degrading enzymes (CWDEs) released during saprophytic and necrotrophic stage of infection of the oil palm host. However, there is a lack of information available on the essentiality of CWDEs in wood-decaying process and pathogenesis of this oil palm pathogen especially at molecular and genome levels.

Methods

In this study, comparative genome analysis was carried out using the G. boninense NJ3 genome to identify and characterize carbohydrate-active enzyme (CAZymes) including CWDE in the fungal genome. Augustus pipeline was employed for gene identification in G. boninense NJ3 and the produced protein sequences were analyzed via dbCAN pipeline and PhiBase 4.5 database annotation for CAZymes and plant-host interaction (PHI) gene analysis, respectively. Comparison of CAZymes from G. boninense NJ3 was made against G. lucidum, a well-studied model Ganoderma sp. and five selected pathogenic fungi for CAZymes characterization. Functional annotation of PHI genes was carried out using Web Gene Ontology Annotation Plot (WEGO) and was used for selecting candidate PHI genes related to cell wall degradation of G. boninense NJ3.

Results

G. boninense was enriched with CAZymes and CWDEs in a similar fashion to G. lucidum that corroborate with the lignocellulolytic abilities of both closely-related fungal strains. The role of polysaccharide and cell wall degrading enzymes in the hemibiotrophic mode of infection of G. boninense was investigated by analyzing the fungal CAZymes with necrotrophic Armillaria solidipes, A. mellea, biotrophic Ustilago maydis, Melampsora larici-populina and hemibiotrophic Moniliophthora perniciosa. Profiles of the selected pathogenic fungi demonstrated that necrotizing pathogens including G. boninense NJ3 exhibited an extensive set of CAZymes as compared to the more CAZymes-limited biotrophic pathogens. Following PHI analysis, several candidate genes including polygalacturonase, endo β-1,3-xylanase, β-glucanase and laccase were identified as potential CWDEs that contribute to the plant host interaction and pathogenesis.

Discussion

This study employed bioinformatics tools for providing a greater understanding of the biological mechanisms underlying the production of CAZymes in G. boninense NJ3. Identification and profiling of the fungal polysaccharide- and lignocellulosic-degrading enzymes would further facilitate in elucidating the infection mechanisms through the production of CWDEs by G. boninense. Identification of CAZymes and CWDE-related PHI genes in G. boninense would serve as the basis for functional studies of genes associated with the fungal virulence and pathogenicity using systems biology and genetic engineering approaches.