Directed evolution of an endoinulinase from Talaromyces purpureogenus toward efficient production of inulooligosaccharides

Insights in inulin binding and inulin oligosaccharide formation by novel multi domain endo-inulinases from Botrytis cinerea

World-wide, pathogenic fungi such as Botrytis cinerea cause tremendous yield losses in terms of food production and post-harvest food decay. Many fungi produce inulin-type oligosaccharides (IOSs) from inulin through endo-inulinases which typically show a two domain structure. B.cinerea lacks a two domain endo-inulinase but contains a three domain structure instead. Genome mining revealed three and four domain (d4) enzymes in the fungal kingdom. Here, three and two domain enzymes were compared in their capacity to produce IOSs from inulin. Hill kinetics were observed in three domain enzymes as compared to Michaelis-Menten kinetics in two domain enzymes, suggesting that the N-terminal extension functions as a carbohydrate binding module. Analysis of the IOS product profiles generated from purified GF6, GF12, GF16 and GF18 inulins and extensive sugar docking approaches led to enhanced insights in the active site functioning, revealing subtle differences between the endo-inulinases from Aspergillus niger and B. cinerea. Improved insights in structure-function relationships in fungal endo-inulinases offer opportunities to develop superior enzymes for the production of specific IOS formulations to improve plant and animal health (priming agents, prebiotics).

Engineering interventions in industrial filamentous fungal cell factories for biomass valorization

Filamentous fungi possess versatile capabilities for synthesizing a variety of valuable bio compounds, including enzymes, organic acids and small molecule secondary metabolites. The advancements of genetic and metabolic engineering techniques and the availability of sequenced genomes discovered their potential as expression hosts for recombinant protein production. Remarkably, plant-biomass degrading filamentous fungi show the unique capability to decompose lignocellulose, an extremely recalcitrant biopolymer. The basic biochemical approaches have motivated several industrial processes for lignocellulose biomass valorisation into fermentable sugars and other biochemical for biofuels, biomolecules, and biomaterials. The review gives insight into current trends in engineering filamentous fungi for enzymes, fuels, and chemicals from lignocellulose biomass. This review describes the variety of enzymes and compounds that filamentous fungi produce, engineering of filamentous fungi for biomass valorisation with a special focus on lignocellulolytic enzymes and other bulk chemicals.

Directed Enzyme Evolution and Encapsulation in Peptide Nanospheres of Quorum Quenching Lactonase as an Antibacterial Treatment against Plant Pathogen

The need to increase agricultural yield has led to an extensive use of antibiotics against plant pathogens, which has resulted in the emergence of resistant strains. Therefore, there is an increasing demand for new methods, preferably with lower chances of developing resistant strains and a lower risk to the environment or public health. Many Gram-negative bacterial pathogens use quorum sensing, a population-density-dependent regulatory mechanism, to monitor the secretion of N-acyl-homoserine lactones (AHLs) and pathogenicity. Therefore, quorum sensing represents an attractive antivirulence target. AHL lactonases hydrolyze AHLs and have potential antibacterial properties; however, their use is limited by thermal instability and durability, or low activity. Here, we demonstrate that an AHL lactonase from the phosphotriesterase-like lactonase family exhibits high activity with the AHL secreted from the plant pathogen Erwinia amylovora and attenuates infection in planta. Using directed enzyme evolution, we were able to increase the enzyme's temperature resistance (T₅₀, the temperature at which 50% of the activity is retained) by 8 °C. Then, by performing enzyme encapsulation in nanospherical capsules composed of tertbutoxycarbonyl-Phe-Phe-OH peptide, the shelf life was extended for more than 5 weeks. Furthermore, the encapsulated and free mutant were able to significantly inhibit up to 70% blossom's infection in the field, achieving the same efficacy as seen with antibiotics commonly used today to treat the plant pathogen. We conclude that specific AHL lactonase can inhibit E. amylovora infection in the field, as it degrades the AHL secreted by this plant pathogen. The combination of directed enzyme evolution and peptide nanostructure encapsulation significantly improved the thermal resistance and shelf life of the enzyme, respectively, increasing its potential in future development as antibacterial treatment.

Understanding the interactive influence of hydrolytic conditions on biocatalytic production of fructooligosaccharides from inulin

Statistical optimization of hydrolytic conditions for the production of fructooligosaccharides (FOSs) from pure inulin using Aspergillus tritici endoinulinase was carried out in a batch system. FOSs yield 99.19% was obtained under the optimized hydrolytic conditions i.e. inulin concentration (7.3%), enzyme load (65 IU), hydrolysis time (13 h) and agitation (100 rpm). The closeness of value of co-efficient of determination (R²) to 1, good agreement between model's predicted and experimental values, low percentage error (<5%), high adequate precision (>4%) and F value (11,634.32), and low Lack of fit (0.60) of the designed model authenticates its fitness. High substrate concentration, low enzyme load and short hydrolysis span justifies efficiency of developed process for the preparation of FOSs from inulin using fungal endoinulinase. TLC chromatographic and densitometry studies confirmed the synthesis of short-chain length FOSs. FOSs preparation contained 33.85% GF2 (ketose), 24.50% GF3 (nystose), 7.26% GF4 (fructofuranosylnystose) and 33.58% FOSs of DP5-9.

Molecular engineering to improve lignocellulosic biomass based applications using filamentous fungi

Lignocellulosic biomass is an abundant and renewable resource, and its utilization has become the focus of research and biotechnology applications as a very promising raw material for the production of value-added compounds. Filamentous fungi play an important role in the production of various lignocellulolytic enzymes, while some of them have also been used for the production of important metabolites. However, wild type strains have limited efficiency in enzyme production or metabolic conversion, and therefore many efforts have been made to engineer improved strains. Examples of this are the manipulation of transcriptional regulators and/or promoters of enzyme-encoding genes to increase gene expression, and protein engineering to improve the biochemical characteristics of specific enzymes. This review provides and overview of the applications of filamentous fungi in lignocellulosic biomass based processes and the development and current status of various molecular engineering strategies to improve these processes.