Enhanced production of prodigiosin by Serratia marcescens FZSF02 in the form of pigment pellets

Background: Prodigiosin has been demonstrated to be an important candidate in investigating anticancer drugs and in many other applications in recent years. However, industrial production of prodigiosin has not been achieved. In this study, we found a prodigiosin-producing strain, Serratia marcescens FZSF02, and its fermentation strategies were studied to achieve the maximum yield of prodigiosin. Results: When the culture medium consisted of 16.97 g/L of peanut powder, 16.02 g/L of beef extract, and 11.29 mL/L of olive oil, prodigiosin reached a yield of 13.622 ± 236 mg/L after culturing at 26 °C for 72 h. Furthermore, when 10 mL/L olive oil was added to the fermentation broth at the 24th hour of fermentation, the maximum prodigiosin production of 15,420.9 mg/L was obtained, which was 9.3-fold higher than the initial level before medium optimization. More than 60% of the prodigiosin produced with this optimized fermentation strategy was in the form of pigment pellets. To the best of our knowledge, this is the first report on this phenomenon of pigment pellet formation, which made it much easier to extract prodigiosin at low cost. Prodigiosin was then purified and identified by absorption spectroscopy, HPLC, and LCMS. Purified prodigiosin obtained in this study showed anticancer activity in separate experiments on several human cell cultures: A549, K562, HL60, HepG2, and HCT116. Conclusions: This is a promising strain for producing prodigiosin. The prodigiosin has potential in anticancer medicine studies.

Enhanced alkaline catalase production by Serratia marcescens FZSF01: enzyme purification, characterization, and recombinant expression

Background: Catalase (CAT) is an important enzyme that degrades H2O2 into H2O and O2. To obtain an efficient catalase, in this study, a new strain of high catalase-producing Serratia marcescens, named FZSF01, was screened and its catalase was purified and characterized. Results: After optimization of fermentation conditions, the yield of catalase produced by this strain was as high as 51,468 U/ml. This catalase was further purified using two steps: DEAE-fast flow and Sephedex-G150. The purified catalase showed a specific activity of 197,575 U/mg with a molecular mass of 58 kDa. This catalase exhibited high activity at 20­70°C and pH 5.0­11.0. Km of the catalase was approximately 68 mM, and Vmax was 1886.8 mol/min mg. This catalase was further identified by LC­MS/MS, and the encoding gene was cloned and expressed in Escherichia coli BL21 (DE3) with a production of 17,267 ± 2037 U/ml. Conclusions: To our knowledge, these results represent one of the highest fermentation levels reported among current catalase-producing strains. This FZSF01 catalase may be suitable for several industrial applications that comprise exposure to alkaline conditions and under a wide range of temperatures.

Effects of open drainage ditch design on bacterial and fungal communities of cold waterlogged paddy soils

A field experiment established in 1980 was conducted to evaluate the effects of open drainage ditch applied for water removal on bacterial and fungal communities of cold waterlogged paddy soils in 2011. In this experiment, traditional plate counting and temperature gradient gel electrophoresis were employed to characterize the abundance and diversity of soil bacterial and fungal communities. Four different distances from the open drainage ditch, 5, 15, 25 and 75 m with different degrees of drainage were designed for this study. Maximum populations of culturable aerobic bacteria and fungi were at 15-m distance while minimum populations were at 75-m distance. Significant differences (p < 0.05) in fungal populations were observed at all distances from open drainage ditch. The highest diversity of the bacterial community was found at a distance of 25 m, while that of the fungal community was observed at a distance of 5 m. Sequencing of excised TGGE bands indicated that the dominant bacteria at 75-m distance belonged to anaerobic or microaerobic bacteria. Relationships between microbial characteristics and soil physicochemical properties indicated that soil pH and available nitrogen contents were key factors controlling the abundance of culturable aerobic bacteria and fungi, while soil water capacity also affected the diversity of fungal community. These findings can provide the references for better design and advanced management of the drainage ditches in cold waterlogged paddy soils.

A comparison of silver staining protocols for detecting DNA in polyester-backed polyacrylamide gel

Eight silver-staining protocols were applied to detect DNA in polyester-backed gels to select the optimal. Results showed important differences in staining quality and that four methods were well-suited for TGGE gels due to high sensitivity and low background, including the Bassam et al. methods, the manufacturer method and our improved method.