Diversity and regioselectivity of O-methyltransferases catalyzing the formation of O-methylated flavonoids

Catalytic divergence of O-methyltransferases shapes the chemo-diversity of polymethoxylated bibenzyls in Dendrobium catenatum

Erianin, crepidatin, and chrysotobibenzyl are typical medicinal polymethoxylated bibenzyls (PMBs) that are commercially produced in Dendrobium species. PMBs' chemo-diversity is mediated by the manifold combinations of O-methylation and hydroxylation in a definite order, which remains unsolved. To unequivocally elucidate the methylation mechanism of PMBs, 15 possible intermediates in the biosynthetic pathway of PMBs were chemically synthesized. DcOMT1-5 were highly expressed in tissues where PMBs were biosynthesized, and their expression patterns were well-correlated with the accumulation profiles of PMBs. Moreover, cell-free orthogonal tests based on the synthesized intermediates further confirmed that DcOMT1-5 exhibited distinct substrate preferences and displayed hydroxyl-group regiospecificity during the sequential methylation process. The stepwise methylation of PMBs was discovered from SAM to dihydro-piceatannol (P) in the following order: P → 3-MeP → 4-OH-3-MeP → 4-OH-3,5-diMeP → 3,3'(4'),5-triMeP → 3,4,4',5-tetraMeP (erianin) or 3,3',4,5-tetraMeP (crepidatin) → 3,3',4,4',5-pentaMeP (chrysotobibenzyl). Furthermore, the regioselectivities of DcOMTs were investigated by ligand docking analyses which corresponded precisely with the catalytic activities. In summary, the findings shed light on the sequential catalytic mechanisms of PMB biosynthesis and provide a comprehensive PMB biosynthetic network in D. catenatum. The knowledge gained from this study may also contribute to the development of plant-based medicinal applications and the production of high-value PMBs.

Modifying flavor profiles of Saccharomyces spp. for industrial brewing using FIND-IT, a non-GMO approach for metabolic engineering of yeast

Species of Saccharomyces genus have played an irreplaceable role in alcoholic beverage and baking industry for centuries. S. cerevisiae has also become an organism of choice for industrial production of alcohol and other valuable chemicals and a model organism shaping the rise of modern genetics and genomics in the past few decades. Today´s brewing industry faces challenges of decreasing consumption of traditional beer styles and increasing consumer demand for new styles, flavors and aromas. The number of currently used brewer's strains and their genetic diversity is yet limited and implementation of more genetic and phenotypic variation is seen as a solution to cope with the market challenges. This requires modification of current production strains or introduction of novel strains from other settings, e.g. industrial or wild habitats into the brewing industry. Due to legal regulation in many countries and negative customer perception of GMO organisms, the production of food and beverages requires non-GMO production organisms, whose development can be difficult and time-consuming. Here, we apply FIND-IT (Fast Identification of Nucleotide variants by DigITal PCR), an ultrafast genome-mining method, for isolation of novel yeast variants with varying flavor profiles. The FIND-IT method uses combination of random mutagenesis, droplet digital PCR with probes that target a specific desired mutation and a sub-isolation of the mutant clone. Such an approach allows the targeted identification and isolation of specific mutant strains with eliminated production of certain flavor and off-flavors and/or changes in the strain metabolism. We demonstrate that the technology is useful for the identification of loss-of function or gain of function mutations in unrelated industrial and wild strains differing in ploidy. Where no other phenotypic selection exists, this technology serves together with standard breeding techniques as a modern tool facilitating a modification of (brewer's) yeast strains leading to diversification of the product portfolio.

Enhancing cellulose hydrolysis via cellulase immobilization on zeolitic imidazolate frameworks using physical adsorption

This study investigates the immobilization of cellulase on zeolitic imidazolate frameworks (ZIFs) by physical adsorption, specifically the ZIF-8-NH2 and Fe3O4@ZIF-8-NH2, to enhance enzymatic hydrolysis efficiency. The immobilization process was thoroughly analyzed, including optimization of conditions and characterization of ZIF carriers and immobilized enzymes. The impacts on the catalytic activity of cellulase under various temperatures, pH levels, and storage conditions were examined. Additionally, the reusability of the immobilized enzyme was assessed. Results showed the cellulase immobilized on Fe3O4@ZIF-8-NH2 exhibited a high loading capacity of 339.64 mg/g, surpassing previous studies. Its relative enzymatic activity was found to be 71.39%. Additionally, this immobilized enzyme system demonstrates robust reusability, retaining 68.42% of its initial activity even after 10 cycles. These findings underscore the potential of Fe3O4@ZIF-8-NH2 as a highly efficient platform for cellulase immobilization, with promising implications for lignocellulosic biorefinery.

A review on the immobilization of bromelain

This review shows the endeavors performed to prepare immobilized formulations of bromelain extract, usually from pineapple, and their use in diverse applications. This extract has a potent proteolytic component that is based on thiol proteases, which differ depending on the location on the fruit. Stem and fruit are the areas where higher activity is found. The edible origin of this enzyme is one of the features that determines the applications of the immobilized bromelain to a more significant degree. The enzyme has been immobilized on a wide diversity of supports via different strategies (covalent bonds, ion exchange), and also forming ex novo solids (nanoflowers, CLEAs, trapping in alginate beads, etc.). The use of preexisting nanoparticles as immobilization supports is relevant, as this facilitates one of the main applications of the immobilized enzyme, in therapeutic applications (as wound dressing and healing components, antibacterial or anticancer, mucus mobility control, etc.). A curiosity is the immobilization of this enzyme on spores of probiotic microorganisms via adsorption, in order to have a perfect in vivo compatibility. Other outstanding applications of the immobilized enzyme are in the stabilization of wine versus haze during storage, mainly when immobilized on chitosan. Curiously, the immobilized bromelain has been scarcely applied in the production of bioactive peptides.

Elucidation and engineering mitochondrial respiratory-related genes for improving bioethanol production at high temperature in Saccharomyces cerevisiae

Industrial manufacturing of bioproducts, especially bioethanol, can benefit from high-temperature fermentation, which requires the use of thermotolerant yeast strains. Mitochondrial activity in yeast is closely related to its overall metabolism. However, the mitochondrial respiratory changes in response to adaptive thermotolerance are still poorly understood and have been rarely utilized for developing thermotolerant yeast cell factories. Here, adaptive evolution and transcriptional sequencing, as well as whole-genome-level gene knockout, were used to obtain a thermotolerant strain of Saccharomyces cerevisiae. Furthermore, thermotolerance and bioethanol production efficiency of the engineered strain were examined. Physiological evaluation showed the boosted fermentation capacity and suppressed mitochondrial respiratory activity in the thermotolerant strain. The improved fermentation produced an increased supply of adenosine triphosphate required for more active energy-consuming pathways. Transcriptome analysis revealed significant changes in the expression of the genes involved in the mitochondrial respiratory chain. Evaluation of mitochondria-associated gene knockout confirmed that ADK1, DOC1, or MET7 were the key factors for the adaptive evolution of thermotolerance in the engineered yeast strain. Intriguingly, overexpression of DOC1 with TEF1 promoter regulation led to a 10.1% increase in ethanol production at 42 °C. The relationships between thermotolerance, mitochondrial activity, and respiration were explored, and a thermotolerant yeast strain was developed by altering the expression of mitochondrial respiration-related genes. This study provides a better understanding on the physiological mechanism of adaptive evolution of thermotolerance in yeast.

Identification of One O-Methyltransferase Gene Involved in Methylated Flavonoid Biosynthesis Related to the UV-B Irradiation Response in Euphorbia lathyris

Flavonoids are ubiquitous polyphenolic compounds that play a vital role in plants' defense response and medicinal efficacy. UV-B radiation is a vital environmental regulator governing flavonoid biosynthesis in plants. Many plants rapidly biosynthesize flavonoids as a response to UV-B stress conditions. Here, we investigated the effects of flavonoid biosynthesis via UV-B irradiation in Euphorbia lathyris. We found that exposure of the E. lathyris callus to UV-B radiation sharply increased the level of one O-methyltransferase (ElOMT1) transcript and led to the biosynthesis of several methylated flavonoids. The methyltransferase ElOMT1 was expressed heterologously in E. coli, and we tested the catalytic activity of recombinant ElOMT1 with possible substrates, including caffeic acid, baicalin, and luteolin, in vitro. ElOMT1 could efficiently methylate when the hydroxyl groups were contained in the core nucleus of the flavonoid. This molecular characterization identifies a methyltransferase responsible for the chemical modification of the core flavonoid structure through methylation and helps reveal the mechanism of methylated flavonoid biosynthesis in Euphorbiaceae. This study identifies the O-methyltransferase that responds to UV-B irradiation and helps shed light on the mechanism of flavonoid biosynthesis in Euphorbia lathyris.