Producing natural vanilla extract from green vanilla beans using a β-glucosidase from Alicyclobacillus acidiphilus

The isolation and identification of Bacillus velezensis ZN-S10 from vanilla (V. planifolia), and the microbial distribution after the curing process

The market value of vanilla beans (Vanilla planifolia) is constantly increasing due to their natural aroma and flavor properties that improve after a curing process, where bacteria colonization plays a critical role. However, a few publications suggest that bacteria play a role in the curing process. Hence, this study aimed to isolate Bacillus sp. that could be used for fermenting V. planifolia while analyzing their role in the curing process. Bacillus velezensis ZN-S10 identified with 16S rRNA sequencing was isolated from conventionally cured V. planifolia beans. A bacteria culture solution of B. velezensis ZN-S10 (1 mL of 1 × 107 CFU mL-1) was then coated on 1 kg of non-cured vanilla pods that was found to ferment and colonize vanilla. PCA results revealed distinguished bacterial communities of fermented vanilla and the control group, suggesting colonization of vanilla. Phylogenetic analysis showed that ZN-S10 was the dominant Bacillus genus member and narrowly correlated to B. velezensis EM-1 and B. velezensis PMC206-1, with 78% and 73% similarity, respectively. The bacterial taxonomic profiling of cured V. planifolia had a significant relative abundance of Firmicutes, Proteobacteria, Cyanobacteria, Planctomycetes, and Bacteroidetes phyla according to the predominance. Firmicutes accounted for 55% of the total bacterial sequences, suggesting their colonization and effective fermentation roles in curing vanilla.

Characterization, Stability and Antioxidant Activity of Vanilla Nano-Emulsion and Its Complex Essential Oil

As a natural flavoring agent, vanilla essential oil has a special aroma and flavor, but its volatility and instability limit its value. Therefore, in this study, vanilla essential oil was compounded with cinnamon essential oil to prepare nano-emulsions (composite nano-emulsions called C/VT and C/VM), and the stability of the composite essential oil emulsions was investigated. Transmission electron microscopy (TEM) images showed that the nano-emulsions were spherical in shape and some flocs were observed in C/VM and C/VT. The results showed that the average droplet sizes of C/VM and C/VT increased only by 14.99% and 15.01% after heating at 100 °C for 20 min, and the average droplet sizes were less than 120 nm after 24 days of storage at 25 °C. Possibly due to the presence of reticulated flocs, which have a hindering effect on the movement of individual droplets, the instability indices of C/VM and C/VT were reduced by 34.9% and 39.08%, respectively, in comparison to the instability indices of C/VM and C/VT. In addition, the results of antioxidant experimental studies showed that the presence of composite essential oil flocs had no significant effect on the antioxidant capacity. These results indicate that the improved stability of the composite essential oil nano-emulsions is conducive to broadening the application of vanilla essential oil emulsions.

Natural deep eutectic solvents-based green extraction of vanillin: optimization, purification, and bioactivity assessment

The sustainable extraction of natural compounds has recently attracted significant attention. The extraction of high-quality natural vanillin in active form is crucial for its efficient use in various industries, but conventional solvents are not suitable for this purpose. The flammability, volatility, and toxicity of organic solvents can harm extraction personnel, and their waste liquid can cause environmental pollution. Natural deep eutectic solvents (NADES) are cost-effective, environmentally friendly, biodegradable, and non-toxic organic alternative to conventional solvents. In this study, 20 different NADES were tested for the sustainable extraction of natural vanillin. Among these, a DES system composed of choline chloride: 1,4-butanediol: lactic acid exhibited the highest extraction rate (15.9 mg/g). Employing response surface methodology (RSM), optimal extraction conditions were determined, yielding a vanillin content 18.5 mg/g with water content of 33.9%, extraction temperature of 64.6°C, extraction time of 32.3 min, and a solid-liquid ratio of 44.9 mg/mL. Subsequently, the optimized NADES system was then assessed for reusability in extracting vanillin from vanilla pods and kraft lignin over three cycles, retaining 43% of its extraction efficiency and demonstrating potential for waste reduction. Purification of vanillin was achieved through chromatography using a non-polar resin SP700, with ethanol as a desorption eluent and a feed solution pH of 4.0, resulting in the highest vanillin purity. HPLC and GC-MS analyses confirmed purity, while antioxidant activity assays (DPPH and ABTS) showcased significant antioxidant activity of the purified vanillin. Moreover, vanillin exhibited notable antimicrobial activity against a panel of food-borne bacteria. This study introduces an environmentally friendly approach to vanillin extraction highlights using NADES, emphasizing the potential for producing high-quality bioactive vanillin with reduced environmental impact. The applicability of NADES systems extends beyond vanillin, offering a versatile method for extracting diverse natural compounds.

Caulobacter segnis Dioxygenase CsO2: A Practical Biocatalyst for Stilbenoid Ozonolysis

Ozonolysis is a useful as well as dangerous reaction for performing alkene cleavage. On the other hand, enzymes are considered a more sustainable and safer alternative. Among them, Caulobacter segnis dioxygenase (CsO2) known so far for its ability to catalyze the coenzyme-free oxidation of vinylguaiacol into vanillin, was selected and its substrate scope evaluated towards diverse natural and synthetic stilbenoids. Under optimized conditions, CsO2 catalyzed the oxidative cleavage of the C=C double bonds of various trans-stilbenes, providing that a hydroxyl moiety was necessary in para-position of the phenyl group (e. g., resveratrol and its derivatives) for the reaction to take place, which was confirmed by modelling studies. The reactions occurred rapidly (0.5-3 h) with high conversions (95-99 %) and without formation of by-products. The resveratrol biotransformation was carried out on 50-mL scale thus confirming the feasibility of the biocatalytic system as a preparative method.

Effect of Microwave and Ultrasound during the Killing Stage of the Curing Process of Vanilla (Vanilla planifolia, Andrews) Pods

The curing process (CP) of Vanilla planifolia pods, which is a long and tedious process, is necessary to obtain the natural vanilla extract. This research evaluated the application of microwave (M) and ultrasound (U) during the "killing" stage of the CP and its effect on vanillin content and β-glucosidase activity. The pods were immersed in a container with water or with moistened samples for the M treatments. In U treatments, the pods were immersed in an ultrasonic bath. After this stage, the samples were subjected to an additional U treatment. The results show that the application of these technologies significantly improves vanillin yield (p < 0.05) and the curing time is reduced to 20 days. U treatments subjected to additional sonication at 38 °C obtain more than double the yield of vanillin regarding control. The effect of M and U on cell structure damage increases with additional sonication, but at 15 min, β-glucosidase inactivation decreases the final yield. Disposition of samples in M also affects the final vanillin content. There is no significant correlation between β-glucosidase and vanillin in the different treatments. The application of M and U with the appropriate parameters reduces the CP time without affecting the compounds of interest.

Unveiling the complete genome sequence of Alicyclobacillus acidoterrestris DSM 3922T, a taint-producing strain

Several species from the Alicyclobacillus genus have received much attention from the food and beverages industries. Their presence has been co-related with spoilage events of acidic food matrices, namely fruit juices and other fruit-based products, the majority attributed to Alicyclobacillus acidoterrestris. In this work, a combination of short and long reads enabled the assembly of the complete genome of A. acidoterrestris DSM 3922T, perfecting the draft genome already available (AURB00000000), and revealing the presence of one chromosome (4,222,202 bp; GC content 52.3%) as well as one plasmid (124,737 bp; GC content 46.6%). From the 4,288 genes identified, 4,004 sequences were attributed to coding sequences with proteins, with more than 80% being functionally annotated. This allowed the identification of metabolic pathways and networks and the interpretation of high-level functions with significant reliability. Furthermore, the additional genes of interest related to spore germination, off-flavor production, namely the vdc cluster, and CRISPR arrays, were identified. More importantly, this is the first complete and closed genome sequence for a taint-producing Alicyclobacillus species and thus represents a valuable reference for further comparative and functional genomic studies.

Study on the Biochemical Characterization and Selectivity of Three β-Glucosidases From Bifidobacterium adolescentis ATCC15703

Three β-glucosidases from Bifidobacterium adolescentis ATCC15703, namely, BaBgl1A, BaBgl3A, and BaBgl3B, were overexpressed in Escherichia coli. The recombinant β-glucosidases were sufficiently purified using Ni²⁺ affinity chromatography, and BaBgl1A exhibited the best purification efficiency with a purification factor of 2.3-fold and specific activity of 71.2 U/mg. Three recombinant β-glucosidases acted on p-nitrophenyl-β-glucopyranoside (pNPβGlc) at around pH 7.0 and 30–50°C. The results of the substrate specificity assay suggested that BaBgl1A acted exclusively as β-1,2-glucosidase, while BaBgl3A and BaBgl3B acted mostly as β-1,3-glucosidase and β-1,4-glucosidase, respectively. The substrate specificity of the three recombinant enzymes was further studied using the ginsenosides Rb1 and Rd as substrates. The results of thin-layer chromatography and high-performance liquid chromatography analyses showed that BaBgl1A exhibited the highest bioconversion ability on Rb1 and Rd, where it hydrolyzed the outer C-3 glucose moieties of Rb1 and Rd into the rare ginsenosides Gypenoside XVII and F₂; BaBgl3A exhibited medium bioconversion ability on Rb1, where it hydrolyzed both the outer C-3 and C-20 glucose moieties of Rb1 into Gyp XVII and Rd; and BaBgl3B was not active on Rb1 and Rd. These β-glucosidases will act as new biocatalytic tools for transforming ginsenosides and preparing active glycosides and aglycone.