Screening a random mutagenesis library of a fungal β-fructofuranosidase using FT-MIR ATR spectroscopy and multivariate analysis

Supplementation of recombinant cellulases with LPMOs and CDHs improves consolidated bioprocessing of cellulose

The increased demand for energy has sparked a global search for renewable energy sources that could partly replace fossil fuel resources and help mitigate climate change. Cellulosic biomass is an ideal feedstock for renewable bioethanol production, but the process is not currently economically feasible due to the high cost of pretreatment and enzyme cocktails to release fermentable sugars. Lytic polysaccharide monooxygenases (LPMOs) and cellobiose dehydrogenases (CDHs) are auxiliary enzymes that can enhance cellulose hydrolysis. In this study, four LPMO and two CDH genes were subcloned and expressed in the Saccharomyces cerevisiae Y294 laboratory strain. SDS-PAGE analysis confirmed the extracellular production of the LPMOs and CDHs in the laboratory S. cerevisiae Y294 strain. A rudimentary cellulase cocktail (cellobiohydrolase 1 and 2, endoglucanase and β-glucosidase) was expressed in the commercial CelluX™ 4 strain and extracellular production of the individual cellulases was confirmed by SDS-PAGE analysis. In vitro cooperation of the CDHs and LPMOs with the rudimentary cellulases produced by strain CelluX™ 4[F4-1] was demonstrated on Whatman filter paper. The significant levels of soluble sugars released from this crystalline cellulose substrate indicated that these auxiliary enzymes could be important components of the CBP yeast cellulolytic system.

Investigating the effect of different inulin-rich substrate preparations from Jerusalem artichoke (Helianthus tuberosus L.) tubers on efficient inulooligosaccharides production

Commercial production of inulooligosaccharides (IOS) relies largely on chicory roots. However, Jerusalem artichoke (JA) tubers provide a suitable alternative due to their high inulin content and low cultivation requirements. In this study, three inulin-rich substrate preparations from JA were investigated to maximize IOS production, namely powder from dried JA tuber slices (Substrate 1), solid residues after extracting protein from the JA powder (Substrate 2) and an inulin-rich fraction extracted from protein extraction residues (Substrate 3). The preferred temperature, pH and inulin substrate concentration were determined after which enzyme dosage and extraction time were optimized to maximize IOS extraction from the three substrates, using pure chicory inulin as benchmark. Under the optimal conditions, Substrate 3 resulted in the highest IOS yield of 82.3% (w/w_inulin). However, IOS production from the Substrate 1 proved more efficient since it renders the highest overall IOS yield (mass of IOS per mass of the starting biomass). In the case of co-production of protein and IOS from the JA tuber in a biorefinery concept, IOS production from the Substrate 2 is preferred since it reduces the inulin losses incurred during substrate preparation. For all the inulin-rich substrates studied, an enzyme dosage of 14.8 U/g_inulin was found to be optimal at reaction time less than 6 h. JA tuber exhibited excellent potential for commercial production of IOS with improved yield and the possible advantage of a reduced biomass cost.

Species discrimination and total polyphenol prediction of porcini mushrooms by fourier transform mid-infrared (FT-MIR) spectrometry combined with multivariate statistical analysis

The plateau specialty agricultural products, wild porcini mushrooms, have great value both as a superb cuisine and as a potential medication. Due to quality different between species added with the fraud behavior in sales process, make poor quality or poisonous sample inflow into the market, which pose a health risk for consumers, but also disrupted the mushroom market. Traditional analysis way is time-consuming and laborious. Therefore, the aim of this study is to develop a way using fourier transform mid-infrared (FT-MIR) spectrometry and data fusion strategies for the fast and accurate species discrimination and predict amount of total polyphenol in four porcini mushrooms. The t-distributed stochastic neighbor embedding based on mid-level data fusion showed two species of Boletus edulis and B. umbriniporus have been identified. The order of correct rate of PLS-DA models was mid-level data fusionq (100%) > mid-level data fusione (97.06%) = mid-level data fusionv (97.06%) = stipes (97.06%) > low-level data fusion (94.12%) > caps (91.18%). The order of correct rate of grid-search support vector machine models was low-level data fusion (100%) > caps (94.12%) > stipes (91.18%), and the order of particle swarm optimization support vector machine was low-level data fusion (100%) > caps (97.06%) > stipes (88.24%). The mid-level data fusionq and low-level data fusion had best discrimination accuracy (100%) allowing each mushroom classed into its real species, which could be used for accurate discrimination of samples. B. edulis mushrooms had highest total polyphenol, with 14.76 mg/g dw and 17.33 in caps and stipes mg/g dw, respectively. The phenols were easier to accumulate in the caps in Leccinum rugosiceps (1.03) and B. tomentipes (1.19), and the opposite phenomenon is observed in B. edulis (0.85) and B. umbriniporus (0.95). The correlation coefficient and residual predictive deviation of best prediction model were 86.76% and 2.40%, respectively, indicating that that there is good relevance between FT-MIR and total polyphenol content, which could be used to predict roughly polyphenols content in mushrooms.

Amberlite IRA 900 versus calcium alginate in immobilization of a novel, engineered β-fructofuranosidase for short-chain fructooligosaccharide synthesis from sucrose

The immobilization of β-fructofuranosidase for short-chain fructooligosaccharide (scFOS) synthesis holds the potential for a more efficient use of the biocatalyst. However, the choice of carrier and immobilization technique is a key to achieving that efficiency. In this study, calcium alginate (CA), Amberlite IRA 900 (AI900) and Dowex Marathon MSA (DMM) were tested as supports for immobilizing a novel engineered β-fructofuranosidase from Aspergillus japonicus for scFOS synthesis. Several immobilization parameters were estimated to ascertain the effectiveness of the carriers in immobilizing the enzyme. The performance of the immobilized biocatalysts are compared in terms of the yield of scFOS produced and reusability. The selection of carriers and reagents was motivated by the need to ensure safety of application in the production of food-grade products. The CA and AI900 both recorded impressive immobilization yields of 82 and 62%, respectively, while the DMM recorded 47%. Enzyme immobilizations on CA, AI900 and DMM showed activity recoveries of 23, 27, and 17%, respectively. The CA, AI900 immobilized and the free enzymes recorded their highest scFOS yields of 59, 53, and 61%, respectively. The AI900 immobilized enzyme produced a consistent scFOS yield and composition for 12 batch cycles but for the CA immobilized enzyme, only 6 batch cycles gave a consistent scFOS yield. In its first record of application in scFOS production, the AI900 anion exchange resin exhibited potential as an adequate carrier for industrial application with possible savings on cost of immobilization and reduced technical difficulty.

Cloning, expression and characterization of a novel fructosyltransferase from Aspergillus niger and its application in the synthesis of fructooligosaccharides

Fructosyltransferases have been used in the industrial production of fructooligosaccharides (FOS).

Semirational Directed Evolution of Loop Regions in Aspergillus japonicus β-Fructofuranosidase for Improved Fructooligosaccharide Production

The Aspergillus japonicus β-fructofuranosidase catalyzes the industrially important biotransformation of sucrose to fructooligosaccharides. Operating at high substrate loading and temperatures between 50 and 60°C, the enzyme activity is negatively influenced by glucose product inhibition and thermal instability. To address these limitations, the solvent-exposed loop regions of the β-fructofuranosidase were engineered using a combined crystal structure- and evolutionary-guided approach. This semirational approach yielded a functionally enriched first-round library of 36 single-amino-acid-substitution variants with 58% retaining activity, and of these, 71% displayed improved activities compared to the parent. The substitutions yielding the five most improved variants subsequently were exhaustively combined and evaluated. A four-substitution combination variant was identified as the most improved and reduced the time to completion of an efficient industrial-like reaction by 22%. Characterization of the top five combination variants by isothermal denaturation assays indicated that these variants displayed improved thermostability, with the most thermostable variant displaying a 5.7°C increased melting temperature. The variants displayed uniquely altered, concentration-dependent substrate and product binding as determined by differential scanning fluorimetry. The altered catalytic activity was evidenced by increased specific activities of all five variants, with the most improved variant doubling that of the parent. Variant homology modeling and computational analyses were used to rationalize the effects of amino acid changes lacking direct interaction with substrates. Data indicated that targeting substitutions to loop regions resulted in improved enzyme thermostability, specific activity, and relief from product inhibition.