During the production of ε-poly-L-lysine (ε-PL) in fed-batch fermentation, the decline of ε-PL synthesis often occurs at middle or late phase of the fermentation. To solve the problem, we adopted two strategies, namely pH shift and feeding yeast extract, to improve the productivity of ε-PL. ε-PL productivity in fermentation by pH shift and feeding yeast extract achieved 4.62 g/(L x d) and 5.16 g/(L x d), which were increased by 27.3% and 42.2% compared with the control ε-PL fed-batch fermentation, respectively. Meanwhile, ε-PL production enhanced 36.95 g/L and 41.32 g/L in 192 h with these two strategies, increased by 27.4% and 42.48% compared to the control, respectively. ε-PL production could be improved at middle or late phase of fed-batch fermentation by pH shift or feeding yeast extract.
Batch Cell Culture Techniques ; Fermentation ; Industrial Microbiology ; Nitrogen ; chemistry ; Polylysine ; biosynthesis

Objective To analyze tumor immune microenvironment and related mechanisms in liver cancer.Methods We included 10 cases of hepatocellular carcinoma,hepatitis B patients and healthy volunteers from January 2015 to December 2017 in Shanxi Grand Hospital.We first detected the peripheral and local GM-CSF level in each group,detected myeloid-derived suppressor cells (MDSCs) GM-CSF and pathway-related protein expression.from liver cancer,tumor margin and normal liver tissue through flow cytometry and immunohistochemistry,Finally,we transfected the CCR4-NOT transcriptional complex subunit 7 (CNOT7) recombinant plasmid in the hepatoma cell line,and then detected the related protein expression.Results There was no significant difference for peripheral blood GM-CSF level between liver cancer group,hepatitis group and control group (P＞0.05).The level of local GM-CSF was (32.2±8.9) ng/L,which was higher than that of hepatocellular carcinoma (9.7±2.7) ng/L and normal liver tissue (11.6±2.9) ng/L.The difference was statistically significant (P＜0.05).The proportion of MDSCs at the edge of the tumor was (9.9 ±3.6) ％,which was higher than that of liver cancer (4.0± 1.5) ％ and normal liver tissue (6.3±2.3) ％,and the difference was statistically significant (P＜0.05).Immunohistochemistrydata was consistent with previous data.Compared with normal liver tissue,CNOT7 and STAT3 were highly expressed in liver cancer tissues,while STAT1 was lowly expressed.HepG2 human hepatoma cells were selected for transfection.Compared with the empty plasmid group,CNOT7 expression was decreased in the knocking out group at the same time STAT1 expression was increased,STAT3 and GM-CSF expression was decreased.Conclusion In hepatocellular carcinoma,the secretion of GM-CSF increased and the number of MDSCs increased.Knocking out CNOT7 reduced GM-CSF secretion and activate the JAK/STAT signaling pathway.