A type D ferulic acid esterase from Streptomyces werraensis affects the volume of wheat dough pastries.

A type D ferulic acid esterase (FAE) was identified in the culture supernatant of Streptomyces werraensis, purified, sequenced, and heterologously produced in E. coli BL21(DE3)Star by co-expressing chaperones groES-groEL (69 U L-1). The unique enzyme with a mass of about 48 kDa showed no similarity to other FAEs, and only moderate homology (78.5%) to a Streptomycete ß-xylosidase. The purified reSwFAED exhibited a temperature optimum of 40 °C, a pH optimum in the range from pH seven to eight and a clear preference for bulky natural substrates, such as 5-O-trans-feruloyl-L-arabinofuranose (FA) and ß-D-xylopyranosyl-(1→2)-5-O-trans-feruloyl-L-arabinofuranose (FAX), compared to the synthetic standard substrate methyl ferulate. Treatment of wheat dough with as little as 0.03 U or 0.3 U kg-1 reSwFAED activity resulted in a significant increase of the bun volume (8.0 or 9.7%, resp.) after baking when combined with polysaccharide-degrading enzymes from Aspergillus. For the first time, the long-standing, but rarely proven positive effect of a FAE in baking was confirmed.

Heterologous production of a feruloyl esterase from Pleurotus sapidus synthesizing feruloyl-saccharide esters.

The feruloyl esterase (FAE) gene EST1 from the basidiomycete Pleurotus sapidus was heterologously expressed in Escherichia coli and Pichia pastoris. Catalytically active recombinant Est1 was secreted using P. pastoris as a host. For expression in P. pastoris, the expression vector pPIC9K was applied. The EST1 gene was cloned with an N-terminal α-mating factor pre-pro sequence and expressed under the control of a methanol inducible alcohol oxidase 1 promotor. Est1 was purified to homogeneity using ion exchange and hydrophobic interaction chromatography. The recombinant Est1 showed optima at pH 5.0 and 50 °C, and released ferulic acid from saccharide esters and from the natural substrate destarched wheat bran. Substrate specificity profile and descriptor-based analysis demonstrated unique properties, showing that Est1 did not fit into the current FAE classification model. Transferuloylation synthesis of feruloyl-saccharide esters was proven for mono- and disaccharides.

A chlorogenic acid esterase with a unique substrate specificity from Ustilago maydis.

An extracellular chlorogenic acid esterase from Ustilago maydis (UmChlE) was purified to homogeneity by using three separation steps, including anion-exchange chromatography on a Q Sepharose FF column, preparative isoelectric focusing (IEF), and, finally, a combination of affinity chromatography and hydrophobic interaction chromatography on polyamide. SDS-PAGE analysis suggested a monomeric protein of ∼71 kDa. The purified enzyme showed maximal activity at pH 7.5 and at 37°C and was active over a wide pH range (3.5 to 9.5). Previously described chlorogenic acid esterases exhibited a comparable affinity for chlorogenic acid, but the enzyme from Ustilago was also active on typical feruloyl esterase substrates. Kinetic constants for chlorogenic acid, methyl p-coumarate, methyl caffeate, and methyl ferulate were as follows: Km values of 19.6 µM, 64.1 µM, 72.5 µM, and 101.8 µM, respectively, and kcat/Km values of 25.83 mM(-1) s(-1), 7.63 mM(-1) s(-1), 3.83 mM(-1) s(-1) and 3.75 mM(-1) s(-1), respectively. UmChlE released ferulic, p-coumaric, and caffeic acids from natural substrates such as destarched wheat bran (DSWB) and coffee pulp (CP), confirming activity on complex plant biomass. The full-length gene encoding UmChlE consisted of 1,758 bp, corresponding to a protein of 585 amino acids, and was functionally produced in Pichia pastoris GS115. Sequence alignments with annotated chlorogenic acid and feruloyl esterases underlined the uniqueness of this enzyme.

Development of a recombinant Arxula adeninivorans cell bioassay for the detection of molecules with progesterone activity in wastewater.

This study describes the development of a bioassay to detect the presence of progesterone and progesterone-like molecules in wastewater samples. The basis of the bioassay is the integration of the human progesterone receptor gene into the yeast Arxula adeninivorans for the constitutive synthesis of the receptor. After incubation, binding of the analyte to the receptor induces the production of a reporter protein. Two reporter proteins were compared for detection parameters such as half-maximal activity (EC50), limit of detection (LoD) and limit of quantification (LoQ). When the extracellular phytase K was used, an EC50 value of 155 ng L(-1) and a LoD of 27 ng L(-1) progesterone were obtained after 4 h incubation, while use of the fluorescent dsRED as the reporter protein, resulted in an EC50 of 320 ng L(-1) and a LoD of 65 ng L(-1) after 20 h incubation. Use of phytase K as the reporter protein offers decreased incubation time and increased sensitivity; however the dsRED reporter system is less labor-intensive. Additionally, the affinity of known agonists and antagonists of the human progesterone receptor was determined. The utility of this bioassay was confirmed by measuring total progesterone equivalent concentration of samples from a wastewater treatment plant. The A. adeninivorans-based transactivation assay was able to measure concentrations of about 311 ng L(-1) in the influent stream but could not detect progesterone activity in effluent. One key feature of the assay is the robustness of A. adeninivorans, which allows sample measurement without any sample preparation.

A novel ACE2 decoy for both neutralization of SARS-CoV-2 variants and killing of infected cells.

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) led to millions of infections and deaths worldwide. As this virus evolves rapidly, there is a high need for treatment options that can win the race against new emerging variants of concern. Here, we describe a novel immunotherapeutic drug based on the SARS-CoV-2 entry receptor ACE2 and provide experimental evidence that it cannot only be used for (i) neutralization of SARS-CoV-2 in vitro and in SARS-CoV-2-infected animal models but also for (ii) clearance of virus-infected cells. For the latter purpose, we equipped the ACE2 decoy with an epitope tag. Thereby, we converted it to an adapter molecule, which we successfully applied in the modular platforms UniMAB and UniCAR for retargeting of either unmodified or universal chimeric antigen receptor-modified immune effector cells. Our results pave the way for a clinical application of this novel ACE2 decoy, which will clearly improve COVID-19 treatment.

Enzymatic mitigation of 5-O-chlorogenic acid for an improved digestibility of coffee.

A p-coumaroyl esterase from Rhizoctonia solani was used to decrease 5-O-chlorogenic acid (5-CQA) content in coffee powder. HPLC-UV showed a decline of up to 98% of 5-CQA after the enzyme treatment. Effects on aroma were determined by means of aroma extract dilution analysis. Flavour dilution factors of treated and control extract differed in four volatile compounds only. Effect on aroma and taste was evaluated by sensory tests. No significant differences were perceived, and no off-flavour nor off-taste was noted. As chlorogenic acids are suspected to cause stomach irritating effects in sensitive people, the enzyme treatment offers a technically feasible approach to improve the quality of coffee beverages by reducing 5-CQA concentration without significantly affecting the aroma and taste profile.

A p-coumaroyl esterase from Rhizoctonia solani with a pronounced chlorogenic acid esterase activity.

Extracellular esterase activity was detected in submerged cultures of Rhizoctonia solani grown in the presence of sugar beet pectin or Tween 80. Putative type B feruloyl esterase (FAE) coding sequences found in the genome data of the basidiomycete were heterologously expressed in Pichia pastoris. Recombinant enzyme production on the 5-L bioreactor scale (Rs pCAE: 3245UL-1) exceeded the productivity of the wild type strain by a factor of 800. Based on substrate specificity profiling, the purified recombinant Rs pCAE was classified as a p-coumaroyl esterase (pCAE) with a pronounced chlorogenic acid esterase side activity. The Rs pCAE was also active on methyl cinnamate, caffeate and ferulate and on feruloylated saccharides. The unprecedented substrate profile of Rs pCAE together with the lack of sequence similarity to known FAEs or pCAEs suggested that the Rs pCAE represents a new type of enzyme. Hydroxycinnamic acids were released from agro-industrial side-streams, such as destarched wheat bran (DSWB), sugar beet pectin (SBP) and coffee pulp (CP). Overnight incubation of coffee pulp with the Rs pCAE resulted in the efficient release of p-coumaric (100%), caffeic (100%) and ferulic acid (85%) indicating possible applications for the valorization of food processing wastes and for the enhanced degradation of lignified biomass.

Cold generation of smoke flavour by the first phenolic acid decarboxylase from a filamentous ascomycete - Isaria farinosa.

A decarboxylase (IfPAD) from the ascomycete Isaria farinosa converted ferulic acid to 4-vinylguaiacol (4-VG), a volatile which imparts the distinct "smoke flavor" of pyrolized wood. The activity was enhanced by adding (E)-ferulic acid to the culture medium and peaked with 3.6 U g-1 mycelium (1 µmol 4-VG min-1). The coding sequence of 543 bp was translated into a 25 kDa protein with a homology of 91 % to putative phenolic acid decarboxylases of its teleomorph, Cordyceps militaris, and Beauveria bassiana, the anamorph of Cordyceps bassiana. Cold shock expression in Escherichia coli yielded 411 U g-1 wet mass. Substrate conversion required a hydroxyl substituent para to a trans-unsaturated C3-side chain of the aromatic ring. Km and kcat/Km values were determined to 0.3 mM and 78.4 mM-1s-1 for p-coumaric acid and 1.9 mM and 45.1 mM-1s-1 for (E)-ferulic acid, respectively. The native enzyme and its recombinant counterpart showed pH-optima at pH 6.0 and pH 5.5, and low temperature optima of 19 °C and 14 °C, respectively. IfPAD produced 4-VG from destarched wheat bran and sugar beet fiber, confirming activity on complex plant biomass. This is the first report on the biochemical characterization of a phenolic acid decarboxylase from a filamentous ascomycete.

Feruloyl esterases from Schizophyllum commune to treat food industry side-streams.

Agro-industrial side-streams are abundant and renewable resources of hydroxycinnamic acids with potential applications as antioxidants and preservatives in the food, health, cosmetic, and pharmaceutical industries. Feruloyl esterases (FAEs) from Schizophyllum commune were functionally expressed in Pichia pastoris with extracellular activities of 6000UL(-1). The recombinant enzymes, ScFaeD1 and ScFaeD2, released ferulic acid from destarched wheat bran and sugar beet pectin. Overnight incubation of coffee pulp released caffeic (>60%), ferulic (>80%) and p-coumaric acid (100%) indicating applicability for the valorization of food processing wastes and enhanced biomass degradation. Based on substrate specificity profiling and the release of diferulates from destarched wheat bran, the recombinant FAEs were characterized as type D FAEs. ScFaeD1 and ScFaeD2 preferably hydrolyzed feruloylated saccharides with ferulic acid esterified to the O-5 position of arabinose residues and showed an unprecedented ability to hydrolyze benzoic acid esters.

Heterologous production and characterization of a chlorogenic acid esterase from Ustilago maydis with a potential use in baking.

Ustilago maydis, an edible mushroom growing on maize (Zea mays), is consumed as the food delicacy huitlacoche in Mexico. A chlorogenic acid esterase from this basidiomycete was expressed in good yields cultivating the heterologous host Pichia pastoris on the 5L bioreactor scale (reUmChlE; 45.9UL(-1)). In contrast to previously described chlorogenic acid esterases, the reUmChlE was also active towards feruloylated saccharides. The enzyme preferred substrates with the ferulic acid esterified to the O-5 position of arabinose residues, typical of graminaceous monocots, over the O-2 position of arabinose or the O-6 position of galactose residues. Determination of kcat/Km showed that the reUmChlE hydrolyzed chlorogenic acid 18-fold more efficiently than methyl ferulate, p-coumarate or caffeate. Phenolic acids were released by reUmChlE from natural substrates, such as destarched wheat bran, sugar beet pectin and coffee pulp. Treatment of wheat dough using reUmChlE resulted in a noticeable softening indicating a potential application of the enzyme in bakery and confectionery.

A halotolerant type A feruloyl esterase from Pleurotus eryngii.

An extracellular feruloyl esterase (PeFaeA) from the culture supernatant of Pleurotus eryngii was purified to homogeneity using cation exchange, hydrophobic interaction, and size exclusion chromatography. The length of the complete coding sequence of PeFaeA was determined to 1668 bp corresponding to a protein of 555 amino acids. The catalytic triad of Ser-Glu-His demonstrated the uniqueness of the enzyme compared to previously published FAEs. The purified PeFaeA was a monomer with an estimated molecular mass of 67 kDa. Maximum feruloyl esterase (FAE) activity was observed at pH 5.0 and 50 °C, respectively. Metal ions (5 mM), except Hg(2+), had no significant influence on the enzyme activity. Substrate specificity profiling characterized the enzyme as a type A FAE preferring bulky natural substrates, such as feruloylated saccharides, rather than small synthetic ones. Km and kcat of the purified enzyme for methyl ferulate were 0.15 mM and 0.85 s(-1). In the presence of 3 M NaCl activity of the enzyme increased by 28 %. PeFaeA alone released only little ferulic acid from destarched wheat bran (DSWB), whereas after addition of Trichoderma viride xylanase the concentration increased more than 20 fold.