Exploring the Successions in Microbial Community and Flavor of Daqu during Fermentation Produced by Different Pressing Patterns.

Daqu can be divided into artificially pressed daqu (A-Daqu) and mechanically pressed daqu (M-Daqu) based on pressing patterns. Here, we compared the discrepancies in physicochemical properties, volatile metabolites, and microbiota features between A-Daqu and M-Daqu during fermentation and further investigated the factors causing those differences. A-Daqu microbiota was characterized by six genera (e.g., Bacillus and Thermoactinomyces), while five genera (e.g., Bacillus and Thermomyces) dominated in M-Daqu. The flavor compounds analysis revealed that no obvious difference was observed in the type of esters between the two types of daqu, and M-Daqu was enriched with more alcohols. The factors related to differences between the two types of daqu were five genera (e.g., Hyphopichia). The functional prediction of microbial communities revealed that the functional discrepancies between the two types of daqu were mainly related to ethanol metabolism and 2,3-butanediol metabolism. This study provided a theoretical basis for understanding the heterogeneity of daqu due to the different pressing patterns.

Metaproteomic investigation of enzyme profile in daqu used for the production of Nongxiangxing baijiu.

Enzymes and microbiota in daqu are essential for the brewing of Nongxiangxing baijiu. Uncover the key enzymes and functional strains in daqu is beneficial to improve the flavor and quality of Nongxiangxing baijiu. In this study, metaproteome technology was employed to determine the enzyme profiles in Nongxiangxing daqu, and strains with high saccharification activity were screened and identified. 933 proteins were identified in daqu, of which 463 belonged to enzymes, including 140 oxidoreductases, 98 transferases, 91 hydrolases, 49 ligases, 41 lyases and 27 isomerases, and hydrolase is the enzyme with the highest abundance in baijiu brewing. Among hydrolases, a total of 36 carbohydrate metabolism-related enzymes (CMEs) were identified, and 12 of them were key enzymes related to glycoside hydrolysis. Four major glycoside hydrolysis enzymes glucoamylase (EC 3.2.1.3), glucan 1,4-alpha-glucosidase (EC 3.2.1.3), glucanase (EC 3.2.1.-) and ß-glucosidase (EC 3.2.1.21) were revealed, and their sources were Byssochlamys spectabilis, Lichtheimia ramosa and Thermoascus aurantiacus, respectively. Then, strains Aspergillus A2, A3, A7, Lichtheimia L1, L4, L5, and Saccharomycopsis S2, S4, S6 with high saccharifying enzyme-producing capacity were screened through culture-dependent approach. Resents presented in this study can further reveal the enzyme profiles and identify the main functional strains in daqu, which can provide theoretical support for the brewing of Nongxiangxing baijiu.

Efficient purification of tetracycline wastewater by activated persulfate with heterogeneous Co-V bimetallic oxides.

The persistence and wide dispersion of antibiotics have a severe impact on the ecological environment. Developing an effective method with universal applicability to remove pollutants is pretty necessary. Herein, a bimetallic oxides (Co3V2O8) heterogeneous material was successfully prepared and used to activate the persulfate (PS) for purification of tetracycline (TC) wastewater. By exploring the reaction conditions and influencing factors, the removal rate of 50 mg⋅L-1 TC reached 87.1% by Co3V2O8/PS system, and the reaction rate constant was up to 0.0271 min-1. As a highly efficient catalyst for the activation of PS, Co3V2O8/PS system produces radicals of SO4•-, •OH, •O2- and 1O2 in the reaction process due to the Co(II) and V(IV) exchange electrons with S2O82- and O2. Simultaneously, the internal electron exchange occurs between Co(II)/Co(III) and V(IV)/V(V), which stabilizes the content of Co(II) and V(IV). This work provides a novel activator for PS activation to degrade contaminants and contributes to a better understanding of the PS activation mechanism by transition compound.

Bacillus aquiflavi sp. nov., isolated from yellow water of strongly flavored Chinese baijiu.

A Gram-stain-positive, strictly aerobic and rod-shaped bacterium, designated as 3 H-10T, was isolated from a yellow water sample collected from the manufacturing process of strong flavor Chinese baijiu in Yibin region of Sichuan province (PR China). Oval endospores were formed at the subtermini of cells with swollen sporangia. The isolate was able to grow at temperatures of 20-45 °C (optimum growth at 37 °C), at pH 6.0-10.0 (optimum growth at pH 8.0) and in the presence of 0-2 % (w/v) NaCl (optimum growth with 0 % NaCl). Ribose was the major cell-wall sugar, and meso-diaminopimelic acid (meso-DAP) was the diagnostic amino acid. The main polar lipids of 3 H-10T included diphosphatidylglycerol (DPG), phosphatidylglycerol (PG) and phosphatidylethanolamine (PE). MK-7 was predominant menaquinone and iso-C15 : 0 (60.7 %) was the major fatty acid. Comparisons of 16S rRNA gene sequence indicated that 3 H-10T was most closely related to Bacillus mesophilus SA4T (96.30 %), Bacillus ginsengihumi Gsoil 114T (96.27 %) and Bacillus shackletonii LMG 18435T (96.27 %). The average nucleotide identity (ANI) values between strain 3 H-10T and the three type strains mentioned above were 69.56, 70.19 and 70.67 %, respectively. The genomic DNA G+C content was 35.4 mol%. On the basis of its phenotypic, chemotaxonomic and phylogenetic properties, strain 3 H-10T represents a novel species of the genus Bacillus, for which the name Bacillus aquiflavi sp. nov. is proposed. The type strain is Bacillus aquiflavi 3 H-10T (=CICC 24755T=JCM 33703T).

Strong adsorption of tetracycline hydrochloride on magnetic carbon-coated cobalt oxide nanoparticles.

The overuse of antibiotics, including tetracycline hydrochloride (TC), seriously threatens human health and ecosystems. In this work, magnetic carbon-coated cobalt oxide nanoparticles (CoO@C) were prepared by one-step annealing method and used as an adsorbent for efficient removal of TC from aqueous solution. The characteristic of the materials was studied by SEM, TEM, and XRD, revealing CoO nanoparticles (≤10 nm) were coated by carbon layer. Several influencial parameters, such as annealing temperature and pH on adsorption of TC, were explored, and found that the maximum adsorption capacity of CoO@C on TC reached as high as 769.43 mg g-1. Furthermore, CoO@C displayed excellent stability and reusability. After four repeated use of the adsorbent, the adsorption capacity still remained at 90% of the initial capacity. The pseudo-second order model and Temkin model proved that it was an exothermic chemical adsorption process. Furthermore, after analysis of FT-IR, Zeta-potential, XPS, the positive charge on the surface of CoO@C forms a strong electrostatic interaction with TC, and in addition, a surface bond is formed between the adsorbent and the TC molecule. This work provides a novel and efficient adsorbent for the purification of TC-containing wastewater.