Search

Objectives: The aim of this work was to study the changes of bacterial cell growth, acetion formation and glucose consumption with fermentation time during batch cultivation., Results: A mathematical model of cell growth, product synthesis, and substrate consumption changes with time during the batch cultivation of acetion was established. By analyzing the fitting curve of the kinetic model, it is found that the calculated value of the model fits well with the experimental value, and the fitting model R2 is greater than 0.98., Conclusions: The kinetic model established in this experiment can better reflect the batch cultivation process of acetion.

Microbial fermentation has become the main method to produce target compound. In this study, a 2-Keto-D-gluconic acid (2-KGA) producing mutant strain was obtained by mutation with rational screening methods. Meanwhile, prodigiosin was produced when the nitrogen source in the medium was changed to peptone and its fermentation conditions were evaluated to achieve high-efficient accumulation. The mutant strain SDSPY-136 was firstly identified as Serratia marcescens by morphological observation and 16S rDNA sequencing. The 2-KGA synthetic capacity of S. marcescens SDSPY-136 was evaluated by shake fermentation with 110 g/L glucose as substrates. For fermentation, 2-KGA yield, conversation rate and purity of SDSPY-136 reached 104.60 g/L, 95.10%, 99.11% in 72 h. The red pigment was extracted from the fermentation broth using acidic methanol and identified as prodigiosin by FT-IR. The optimal conditions were as follows: glycerol 20 g/L, peptone 20 g/L, MgSO415 g/L, pH 6.0, a 2% (v/v) inoculum, 30 °C and 200 rpm of shaking culture. Eventually, prodigiosin reached a yield of 9.89 g/Lafter shake culturing for 50 h under this condition. The mutant S. marcescens SDSPY-136 was shown to be promising for 2-KGA and prodigiosin production and a suitable object for prodigiosin metabolism research of S. marcescens. [ABSTRACT FROM AUTHOR]

Extrusion-pretreated Apios fortunei was used for yellow wine fermentation. To investigate the effect of thermostable α-amylase on the physicochemical and antioxidant properties of extruded A. fortunei , we used different enzyme concentrations (0–5‰). Enzymatic extrusion increased the degree of gelatinization (84.23–99.99%), water solubility index (28.09–62.75%), reducing sugar content (74.82–263.39 mg/g) and decreased water absorption index (3.25–2.09 g/g) and viscosity (<20 cP) of A. fortunei, these may be beneficial for fermentation. X -ray diffraction and Fourier transform infrared spectroscopy detected that the ordered degree of starch structure decreased with increased enzyme concentration. Molecular-weight analysis indicated that enzyme concentrations of more than 0.5‰ had limited promotion on starch degradation. Scanning electron microscopy observed the eroded surface and holes caused by enzymolysis in enzymatically extruded samples. Enzymatic extrusion increased the phenolic content and antioxidant properties of the samples. Relatively high fermentation efficiency (74.23%) and antioxidant properties (75.87, 76.21 and 203.32 mg of Trolox equivalents/L for DPPH, ABTS and FRAP values, respectively) were observed in wines fermented by extruded samples with 5‰ enzyme. The results indicated that the advantages of enzymatic extrusion in starch degradation and improving the antioxidant properties of A. fortunei could be extended to yellow wine fermentation. • The ordered degree of starch structure decreased with increased enzyme addition. • Enzyme concentrations more than 0.5‰ had limited promotion on starch degradation. • The enzyme increased phenolic content and antioxidant properties of Apios fortunei. • Apios fortunei treated by enzymatic extrusion was more suitable for fermentation. [ABSTRACT FROM AUTHOR]