Effects of ozone on activated sludge: performance of anaerobic digestion and structure of the microbial community.

The treatment and disposal of activated sludge are currently challenging tasks in the world. As a common biological engineering technology, biological fermentation exists with disadvantages such as low efficiency and complex process. Ozone pretreatments are commonly applied to improve this problem due to their high efficiency and low cost. In this study, the significant function of ozone in anaerobic fermentation gas production was verified with excess sludge. Compared with other untreated sludge, ozone pretreatment can effectively degrade activated sludge. After ozone treatment and mixing with primary sludge, the methane production of excess sludge increased by 49.30 and 50.78%, and the methanogenic activity increased by 69.99 and 73.83%, respectively. The results indicated that the mixing of primary sludge with excess sludge possessed synergistic effects, which contributed to the anaerobic fermentation of excess sludge. The results of microbial community structure exhibited that methanogenic processes mainly involve hydrogenogens, acidogens and methanogens. The relative abundance of both bacteria and microorganisms changed significantly in the early stage of hydraulic retention time, which coincided exactly with the gas production stage. This study provided a feasible pretreatment strategy to improve sludge biodegradability and revealed the role of microorganisms during anaerobic digestion.

Preparation and characterization of 3D-printed antibacterial hydrogel with benzyl isothiocyanate.

Benzyl isothiocyanate (BITC) is an isothiocyanate of plant origin, especially the mustard family, which has good antibacterial properties. However, its applications are challenging due to its poor water solubility and chemical instability. We used food hydrocolloids, including xanthan gum, locust bean gum, konjac glucomannan, and carrageenan as three-dimensional (3D)-printing food ink base and successfully prepared 3D-printed BITC antibacterial hydrogel (BITC-XLKC-Gel). The characterization and fabrication procedure of BITC-XLKC-Gel was studied. The results show that BITC-XLKC-Gel hydrogel has better mechanical properties by low-field nuclear magnetic resonance (LF-NMR), mechanical properties, and rheometer analysis. The strain rate of BITC-XLKC-Gel hydrogel is 76.5%, which is better than that of human skin. Scanning electron microscope (SEM) analysis showed that BITC-XLKC-Gel has uniform pore size and provides a good carrier environment for BITC carriers. In addition, BITC-XLKC-Gel has good 3D-printing performance, and 3D printing can be used for customizing patterns. Finally, inhibition zone analysis showed that the BITC-XLKC-Gel added with 0.6% BITC had strong antibacterial activity against Staphylococcus aureus and the BITC-XLKC-Gel added with 0.4% BITC had strong antibacterial activity against Escherichia coli. Antibacterial wound dressing has always been considered essential in burn wound healing. In experiments that simulated burn infection, BITC-XLKC-Gel showed good antimicrobial activity against methicillin-resistant S. aureus. BITC-XLKC-Gel is a good 3D-printing food ink attributed to strong plasticity, high safety profile, and good antibacterial performance and has great application prospects.

Encapsulation of Benzyl Isothiocyanate with ß-Cyclodextrin Using Ultrasonication: Preparation, Characterization, and Antibacterial Assay.

Benzyl isothiocyanate (BITC) is widely utilized in multiple biomedical fields, due to its significant antibacterial properties and low toxicity. However, poor water solubility and pungent odor has limited its application in the food industry. In this study, we first prepared inclusion complexes of BITC in GLU-ß-CD and HP-ß-CD using ultrasound, which is able to overcome the hindrance of poor water solubility and high volatility. Then, the BITC-ß-CD inclusion complexes were characterized by using high-performance liquid chromatography (HPLC), nuclear magnetic resonance hydrogen spectra (1H-NMR), infrared absorption spectra (IR), and differential scanning calorimetry (DSC) to confirm their stability. Further, the evaluation of antibacterial and antitumor effects of the BITC-ß-CD inclusion complexes showed that they had great bactericidal activity against both Escherichia coli and Staphylococcus aureus cells, and also inhibited the growth of HepG2 cells in vitro. In addition, our results indicated that BITC-ß-CD complexes were able to inhibit the growth of S. aureus in broccoli juice and extend the shelf life of broccoli juice, demonstrating the potential of ß-cyclodextrin to improve the stability and controlled release of BITC. Taken together, our results show that BITC-ß-CD complexes have good potential for application in the food industry.

Transcriptome Analysis and Weighted Gene Co-expression Network Reveal Multitarget-Directed Antibacterial Mechanisms of Benzyl Isothiocyanate against Staphylococcus aureus.

Staphylococcus aureus can cause many diseases and has a strong tendency to develop resistance to multiple antibiotics. In this study, benzyl isothiocyanate (BITC) was shown to have an excellent inhibitory effect on S. aureus ATCC25923 and methicillin-resistant S. aureus strains, with a minimum inhibitory concentration of 10 µg/mL. Under a scanning electron microscope, shrinkage and lysis of the cellular envelope were observed when exposed to BITC, and a bactericidal mode of BITC against S. aureus was further confirmed through flow cytometry. Additionally, the RNA profiles of S. aureus cells exposed to BITC indicated a violent transcriptional response to BITC. Through Kyoto Encyclopedia of Genes and Genomes analysis, it was found that many pathways involving bacterial survival were significantly affected, such as RNA degradation, oxidative phosphorylation, arginine biosynthesis, and so forth. A gene co-expression network was constructed using weighted gene co-expression network analysis, and six biologically meaningful co-expression modules and 125 hub genes were identified from the network. Among them, EfeB, GroES, SmpB, and Lsp were possibly targeted by BITC, leading to the death of S. aureus. Our results indicated a great potential of BITC to be applied in food safety and pharmaceuticals, highlighting its multitarget-directed bactericidal effects on S. aureus.

Accelerating vinegar aging by combination of ultrasonic and magnetic field assistance.

Most fermented foods need a natural aging process to enrich desired flavours. This process is normally the bottleneck for cost-effective production. Therefore, it is desirable to accelerate the process and obtain products with the same flavour profile. Here, we used physical interventions (ultrasonic field, alternating magnetic field, or combination of both) to assist the aging process with naturally brewed vinegar as a case example. Flavour profiles of different physical-assisted aging process were compared with that of the naturally aged vinegar by using gas-chromatography mass-spectrometry (GC-MS) and electronic nose. Principal component analysis (PCA) and Pearson correlation analyses show that ultrasonic and alternating magnetic fields treatment could accelerate the aging process of vinegar. The highest accelerating aging effect was combination of ultrasonic and magnetic field followed by individual ultrasonic or magnetic field and natural process (combination of ultrasonic and magnetic field > ultrasonic or magnetic field individual > natural process). These results suggest that physical field intervention could potentially be used for acceleration of aging of fermented products without affecting flavour quality.