The Mutagenesis of Lactobacillus Thermophilus for Enhanced L-(+)-Lactic Acid Accumulation Induced by Heavy Ion Irradiation

ABSTRACT Screening promising L. thermophiles with high productivity, high efficiency and strong adaptability are very important in lactic acid industry. For this purpose, 80MeV/u carbon ions were applied to irradiate L. thermophiles. After high-throughput screening, a mutant, named SRZ50, was obtained. Different carbon sources or nitrogen sources were provided to investigate carbon or nitrogen source utilization between mutant SRZ50 and wild type, and different fermentation periods were also chose to study fermentation characteristic between mutant SRZ50 and wild type. The results showed that mutant SRZ50 exhibited the enhanced L-(+)-lactic acid production from wild type. When glucose or fructose was the sole carbon source, the L(+)-lactic acid production by mutant SRZ50 was both the highest, respectively, 23.16 ± 0.72 g/L or 23.24 ± 0.66 g/L, which had a significant increase from that of wild type (P<0.01), following obvious increase in biomass (P<0.05). When yeast powder was the sole nitrogen source, it can promote mutant SRZ50 to accumulate the highest L-(+)-lactic acid accumulation, which also had a significant increase from that of wild type (P<0.01). Under different fermentation periods, it was obtained that mutant SRZ50 all exhibited significant increase in L-(+)-lactic acid accumulation from wild type. In conclusion, a mutant strain with improved production profiles for L-(+)-lactic acid, was obtained, indicating that heavy ions can be an efficient tool to improve metabolic product accumulations in microbes.

Simulated microgravity conditions and carbon ion irradiation induce spermatogenic cell apoptosis and sperm DNA damage / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To investigate the effect of simulated microgravity and carbon ion irradiation (CIR) on spermatogenic cell apoptosis and sperm DNA damage to the testis of male Swiss Webster mice, and assess the risk associated with space environment.</p><p><b>METHODS</b>Sperm DNA damage indicated by DNA fragmentation index (DFI) and high DNA stainability (HDS) was measured by sperm chromatin structure assay (SCSA). Apoptosis of spermatogenic cells was detected by annexin V-propidium iodide assay. Bax (the expression levels of p53) and proliferating cell nuclear antigen (PCNA) were measured by immunoblotting; p53 and PCNA were located by immunohistology.</p><p><b>RESULTS</b>HDS, DFI, apoptosis index, and the expression levels of p53 and Bax were detected to be significantly higher in the experimental groups (P<0.05) compared with those in the control group; however, the PCNA expression varied to a certain degree. p53- and PCNA- positive expression were detected in each group, mainly in relation to the spermatogonic cells and spermatocytes.</p><p><b>CONCLUSION</b>The findings of the present study demonstrated that simulated microgravity and CIR can induce spermatogenic cell apoptosis and sperm DNA damage. Sperm DNA damage may be one of the underlying mechanisms behind male fertility decline under space environment. These findings may provide a scientific basis for protecting astronauts and space traveler's health and safety.</p>

The Effect of Ion-irradiation and Active Macrophage on Vascular Endothelial Cell / 中国医师杂志

Objective To investigate the effect of strong ion-irradiation and active macrophage on vascular endothelial cells. Methods The vascular endothelial cells(ECV-304) were divided into 3 groups: ECV304(A), ECV-304 with radiation (B)and ECV-304 with active macrophage U937 and radiation(C). The survival rates, cell cycle and apoptosis of ECV-304 were determined 48 hours after irradiation. The concentrations of TGF-?1 and VEGF in the cultured supernatant were determined by ELISA method.The protein expression of the endothelial receptor KDR in ECV-304 cells was detected by immunofluorescence and flow-cytometry while its mRNA expression was detected by RT-PCR. Results After high dose of ion-irrdiation, the cellular proliferation activity decreased, apopototic cells increased and the cell ratio in G2/M phase increased.In addition,The secretion of VEGF and TGF-?1 was promoted with the increased KDR expression. Active macrophages could alleviate the decrease of cellular proliferation and the increase of apoptotic cells and cell ratio in G2/M phase induced by ion-irriation.Furthermore,the VEGF secretion and the KDR expression were enhanced and the secretion of TGF-?1 was inhibited by the active macrophages. Conclusions Ion irradiation could induce the decrease of cellular proloferation, the increase of apoptotic cells and the cells in G2/M phase.This might partly be related to the inhibiting roles of TGF-?1 secreted by the ECV-304 cells.Active macrophages might protect the endothelial cells from radiation injury.