Monacolin K (MK) produced by Monascus spp. is mostly used to regulate cholesterol level, while it can be contaminated by citrinin, a mycotoxin yielded by some Monascus strains. To develop production of citrinin-free MK, an M . sp. MS-1 strain, identified as M. pilosus by morphologies and internal transcribed spacer sequences analysis, was isolated from red fermented rice. After 14 days of fermentation, yields of citrinin-free MK could be up to 0.58 mg/mL and 16.45 mg/g in liquid- and solidstate fermentation products under optimal conditions, respectively. Further determination revealed that no citrinin biosynthesis related genes such as ctnA , pksCT , ctnE , and ctnR were detected. Thus, HPLC combined with citrinin-related gene analyses can be used for rapid screening of non-citrinin production Monascus strains.
Hongzhe Li,Jiazhi Ding,Longji Zhu,Fei Xu,Wenjing Li,Yanpo Yao,Li Cui
Application of agricultural waste such as rapeseed meal (RM) is regarded as a sustainable way to improve soil phosphorus (P) availability by direct nutrient supply and stimulation of native phosphate-solubilizing microorganisms (PSMs) in soils. However, exploration of the in situ microbial P solubilizing function in soils remains a challenge. Here, by applying both phenotype-based single-cell Raman with D 2 O labeling (Raman-D 2 O) and genotype-based high-throughput chips targeting carbon, nitrogen and P (CNP) functional genes, the effect of RM application on microbial P solubilization in three typical farmland soils was investigated. The abundances of PSMs increased in two alkaline soils after RM application identified by single-cell Raman D 2 O. RM application reduced the diversity of bacterial communities and increased the abundance of a few bacteria with reported P solubilization function. Genotypic analysis indicated that RM addition generally increased the relative abundance of CNP functional genes. A correlation analysis of the abundance of active PSMs with the abundance of soil microbes or functional genes was carried out to decipher the linkage between the phenotype and genotype of PSMs. Myxococcota and C degradation genes were found to potentially contribute to the enhanced microbial P release following RM application. This work provides important new insights into the in situ function of soil PSMs. It will lead to better harnessing of agricultural waste to mobilize soil legacy P and mitigate the P crisis. Impact statement Stimulation of native soil microorganisms to release soil P stocks is a sustainable means of agricultural production, but faces a major challenge in terms of the deciphering of in situ microbial phosphorus (P) solubilization functions. In this study, single-cell Raman spectroscopy and carbon, nitrogen and P (CNP) functional gene chips were used to reveal the phenotypes and genotypes of microbial P solubilization function in three farmland soils amended with agricultural waste of rapeseed meal (RM). Effects of RM on soil properties, active phosphate-solubilizing bacteria, and CNP functional genes that may contribute to P solubilization were revealed, providing important insights into the use of agricultural waste to improve P utilization efficiency.
Jian-Jiang Lu,Qi Shen,Xiao-Ying Li,Fei-Yun Sun,Jun-Bo Yi,Wen-Yi Dong,Wei-Jia Yan,Hong Du,Jia-Le Mu
Undesired long start-up time and unstable denitrification performance are major bottlenecks for engineering application of methane-based membrane biofilm reactors (MBfRs). In this study, two surface-manipulated membranes by respectively coating dopamine (DOPA) and grafting methoxy-poly(ethyleneglycol)-amine (mPEG-NH 2 ) onto the base polypropylene (PP) membrane were prepared, and for the first employed to aerobic methane oxidation coupled to denitrification (AME-D) process in MBfRs for quick biofilm formation and improving denitrification performance. The experiments demonstrated that the modified membranes, especially for PP/DOPA/mPEGNH 2 membrane, accelerated biofilm formation, and then shorten above 31% start-up time compared to the base PP membrane. Meanwhile, the biofilm detachment resistances also improved in the MBfRs employing the modified membrane. Extended Deraguin-Landau-Verwery-Oxerbeek (XDLVO) theory analysis indicated these benefits mainly attribute to enhanced interfacial interaction energy, which is significant to microbial initial attachment onto membrane surface. 16S rRNA gene analysis demonstrated the modified membrane also preferentially increased the abundances of key microorganisms at initial stage. These findings revealed the importance of quick biofilm formation and robust detachment resistance by involving surface-manipulated membranes onto maintaining MBfRs efficiency and stability.
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