Effect of initial pH, different nitrogen sources, and cultivation time on the production of yellow or orange Monascus purpureus pigments and the mycotoxin citrinin

Monascus purpureus was grown in submerged liquid culture using ammonium sulfate, sodium nitrate, and peptone as nitrogen sources while initial medium pH was adjusted to 2.5, 5.5, 6.5, or 8.0. The combined effect of culture pH and nitrogen source on the biosynthesis of yellow (ankaflavin and monascin) and orange (rubropunctatin and monascorubrin) pigments, plus the mycotoxin citrinin, was evaluated chromatographically. Optimum cultivation conditions, that is, initial pH 2.5 and 8.8 g/L peptone as a nitrogen source, resulted in high levels of production of yellow and orange pigments (sum of pigment concentration 1,138 mg/L) and negligible citrinin concentration (2 mg/L)

Continuous production of n-butanol by Clostridium pasteurianum DSM 525 using suspended and surface-immobilized cells

For n-butanol production by Clostridium pasteurianum DSM 525, a modified reinforced Clostridium medium was used, where glucose was alternated with glycerol and two kinds of continuous fermentation were tested using suspended and surface immobilized cells on corn stover pieces. A steady state, with butanol productivity of 4.2g/Lh, was reached during the packed-bed continuous fermentation at a dilution rate of 0.44h(-1). The average n-butanol concentration, yield and the ratio of n-butanol/liquid by-products were 10.4g/L, 33 % and 2.5, respectively. Unexpectedly, during continuous fermentation with suspended cells, at a dilution rate of 0.01h(-1), steady-state was not achieved and regular oscillations occurred in all measured variables, i.e. concentrations of glycerol, products and the number of cells stained with the fluorescent dyes carboxy fluorescein diacetate and propidium iodide. A possible explanation for oscillatory/steady-state behavior of suspended/surface-attached cells, respectively, may be specific butanol toxicity (toxicity per cell), which was higher/lower in respective cases, and which might be caused by lower/higher cell numbers respectively in both systems

Transcriptional analysis of amino acid, metal ion, vitamin and carbohydrate uptake in butanol-producing Clostridium beijerinckii NRRL B-598.

In-depth knowledge of cell metabolism and nutrient uptake mechanisms can lead to the development of a tool for improving acetone-butanol-ethanol (ABE) fermentation performance and help to overcome bottlenecks in the process, such as the high cost of substrates and low production rates. Over 300 genes potentially encoding transport of amino acids, metal ions, vitamins and carbohydrates were identified in the genome of the butanol-producing strain Clostridium beijerinckii NRRL B-598, based on similarity searches in protein function databases. Transcriptomic data of the genes were obtained during ABE fermentation by RNA-Seq experiments and covered acidogenesis, solventogenesis and sporulation. The physiological roles of the selected 81 actively expressed transport genes were established on the basis of their expression profiles at particular stages of ABE fermentation. This article describes how genes encoding the uptake of glucose, iron, riboflavin, glutamine, methionine and other nutrients take part in growth, production and stress responses of C. beijerinckii NRRL B-598. These data increase our knowledge of transport mechanisms in solventogenic Clostridium and may be used in the selection of individual genes for further research

Additional file 6: of Transcription profiling of butanol producer Clostridium beijerinckii NRRL B-598 using RNA-Seq

Differential expression analysis. Complete results of differential expression analysis using DESeq2. (XLSX 2287 kb

Additional file 3: of Transcription profiling of butanol producer Clostridium beijerinckii NRRL B-598 using RNA-Seq

Putative active genes misidentified as pseudogenes due to assembly errors. (PDF 210 kb

Additional file 4: of Transcription profiling of butanol producer Clostridium beijerinckii NRRL B-598 using RNA-Seq

Circular plots showing average coverage of the genome by RNA-Seq reads in all six time points. The outermost and the second outermost circles represent positions of genes on the forward (red) and reverse (blue) strands respectively. The third circle (green) stands for pseudogenes. The yellow peak and shading area represents transcription greater than the average and violet lower than average. Floating window of 10,000 bp with step of 200 bp was used to render the shading area. (PDF 701 kb

Additional file 8: of Transcription profiling of butanol producer Clostridium beijerinckii NRRL B-598 using RNA-Seq

COG functional categories of differential expressed genes. Barplots showing the number of COG categories associated with differentially expressed genes between adjacent time points. (PDF 226 kb

Additional file 2: of Transcription profiling of butanol producer Clostridium beijerinckii NRRL B-598 using RNA-Seq

Silent pseudogenes. (PDF 195 kb

Additional file 7: of Transcription profiling of butanol producer Clostridium beijerinckii NRRL B-598 using RNA-Seq

Dotplot of C. beijerinckii NRRL B-598 and C. beijerinckii NCIMB 8052 genome. Dotplots showing that no major rearrangement between the two strains are present. (PDF 315 kb