Search

The large molecular weight and high viscosity of natural konjac glucomannan (KGM) limit its industrial application. Microbial degradation of low-molecular-weight KGM has health benefits and various biological functions; however, the available KGM strains used in the industry have microbial contamination and low degradation efficiencies. Therefore, exploring novelly adaptable strains is critical for industrial processes. Here, the Bacillus licheniformis Z7-1 strain isolated from decaying konjac showed high efficiency for KGM degradation. The monosaccharide composition of the degradation products had a reduced molar ratio of mannose to glucose, indicating that Z7-1 preferentially degraded glucose in KGM. The degraded component was further characterized by ESI-MS, Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM), and it also exhibited good antibacterial activity against various food-spoilage bacteria. Genome sequencing and zymolytic analysis revealed that abundant carbohydrate-active enzymes exist in the Z7-1 genome, with at least five types of extracellular enzymes responsible for KGM degradation, manifesting multi-enzyme synergetic action. The extracellular enzymes had significant thermal stability, indicating their potential application in industry. This study provides an alternative method for obtaining low-molecular-weight KGM with antibacterial functions and supports foundational knowledge for its development as a biocatalyst for the direct conversion of biomass polysaccharides into functional components.

Stenotrophomonas maltophilia is a major threat to the food industry and human health owing to its strong protease production and biofilm formation abilities. However, information regarding regulatory factors or potential mechanisms is limited. Herein, we observed that temperature differentially regulates biofilm formation and protease production, and a cAMP receptor-like protein (Clp) negatively regulates thermosensor biofilm formation, in contrast to protease synthesis. Among four c-di-GMP-related two-component systems (TCSs), promoter fusion analysis revealed that clp transcription levels were predominantly controlled by LotS/LotR, partially controlled by both RpfC/RpfG and a novel TCS Sm0738/Sm0737, with no obvious effect caused by Sm1912/Sm1911. Biofilm formation in Δclp and ΔTCSs strains suggested that LotS/LotR controlled biofilm formation in a Clp-mediated manner, whereas both RpfC/RpfG and Sm0738/Sm0737 may occur in a distinct pathway. Furthermore, enzymatic activity analysis combined with c-di-GMP level indicated that the enzymatic activity of c-di-GMP-related metabolism proteins may not be a vital contributor to changes in c-di-GMP level, thus influencing physiological functions. Our findings elucidate that the regulatory pathway of c-di-GMP-related TCSs and Clp in controlling spoilage or the formation of potentially pathogenic factors in Stenotrophomonas expand the understanding of c-di-GMP metabolism and provide clues to control risk factors of S. maltophilia in food safety.

Lycorine is a kind of natural active ingredient with a strong antitumor effect. In this study, folate ligand-conjugated polyethylene glycol-block-poly(l-lactide) (PEG-PLLA) nanoparticles (FA-PEG-PLLA NPs) were designed to deliver lycorine to enhance its anti-glioma activity. The successful preparation of the FA-PEG-PLLA polymer was confirmed by 1H-NMR, FT-IR, XRD, TGA, and DSC. The optimal formulation for LYC@FA-PEG-PLLA NPs was determined by response surface analysis as follows: sodium dodecyl sulfate (SDS) of 1%, carrier material of 0.03 g, organic phase volume of 3 mL, and ultrasonic power of 20%. The LYC@FA-PEG-PLLA NPs exhibited an encapsulation efficiency of 83.58% and a particle size of 49.71 nm, demonstrating good stability. Hemolysis experiments, MTT assays, and cell scratch assays revealed excellent biocompatibility of FA-PEG-PLLA and superior anti-glioma activity of LYC@FA-PEG-PLLA NPs compared to the raw drug. Additionally, cell apoptosis assays, ROS experiments, and western blot analysis demonstrated that LYC@FA-PEG-PLLA NPs contributed to cell apoptosis by inducing ROS generation and increasing the expression of NF-κB inhibitory protein IκBα. These results suggested that LYC@FA-PEG-PLLA NPs hold promise for glioma treatment.