@article {44421,
	title = {Zinc supplementation decreases galactosylation of recombinant IgG in CHO cells},
	journal = {Applied Microbiology and Biotechnology},
	year = {2018},
	month = {MAY},
	pages = {1-11},
	type = {Journal Article},
	abstract = {<p>Trace element composition of culture medium can be altered to modulate glycoform of recombinant glycoproteins. In this study, we show that Zn2+ supplementation at or above 100 μM decreases galactosylation of recombinant IgG expressed in Chinese Hamster Ovary cells. This decrease in galactosylation is not due to reduced galactosyltransferase expression. This effect persists upon supplementation of galactose and uridine to the culture, indicating that it may not be due to reduced UDP-Gal availability. Measurements of galactosyltransferase activity in the cell lysate show that activity decreases with increasing Zn2+/Mn2+ ratio. This suggests that one possible explanation of the effect of Zn2+ may be reduced intracellular galactosyltransferase activity due to increase in Zn2+/Mn2+ ratio. Consistent with this, the decrease in galactosylation of IgG could be reversed by supplementation of Mn2+ (a cofactor of galactosyltransferase) which increases intracellular Mn2+ content. Measurement of total intracellular Zn2+ content, however, indicates no significant upregulation of total intracellular Zn2+ content and no significant downregulation of intracellular Mn2+ content with Zn2+ supplementation. One possible explanation could be that cellular detoxification response to higher extracellular Zn2+ concentration might lead to changes in intracellular distribution of Mn2+. In this case, Zn2+ supplementation would be expected to interfere with other known effects of Mn2+. Indeed, the previously reported increase in high mannose glycans upon Mn2+ supplementation in the absence of glucose is reversed by Zn2+ supplementation. This study also suggests the use of Mn2+ supplementation as a strategy to overcome the effect of lot-to-lot variability in trace element concentrations on galactosylation.</p>},
	keywords = {CHO cells, glycosylation, manganese, Trace metals, zinc},
	issn = {1757598},
	doi = {10.1007/s00253-018-9064-8},
	author = {Prabhu, Anuja},
	editor = {Gadre, Ramchandra}
}
@article {46929,
	title = {Enhancing titers and productivity of rCHO clones with a combination of an optimized fed-batch process and ER-stress adaptation},
	journal = {Journal of Biotechnology},
	volume = {311},
	year = {2020},
	month = {MAR},
	pages = {49-58},
	type = {Article},
	abstract = {<p>To increase the productivity of rCHO cells, many cell engineering approaches have been demonstrated that over-express or knockout a specific gene to achieve increased titers. In this work, we present an alternate approach, based on the concept of evolutionary adaptation, to achieve cells with higher titers. rCHO cells, producing a monoclonal antibody, are adapted to ER-stress, by continuous culturing under increasing concentration of tunicamycin. A sustained higher productivity of at-least 2-fold was achieved in all the clones, in a concentration-dependent manner. Similarly, a 1.5-2 fold increase in final titers was also achieved in the batch culture. Based on metabolic analysis of the adapted cells, a fed-batch process was designed where significantly higher titersare achieved as compared to control. Metabolic flux analysis is employed in addition with gene expression analysis of key genes to understand the basis of increased performance of the adapted cells. Overall, this work illustrates how process modifications and cellular adaptation can be used in synergy to drive up product titers.</p>
},
	keywords = {Adaptive laboratory evolution, CHO cells, ER-stress, Fed-batch, Increased productivity and titers, Recombinant protein production, UPR pathway},
	issn = {0168-1656},
	doi = {10.1016/j.jbiotec.2020.02.008},
	author = {Chandrawanshi, Vikas and Kulkarni, Rohan and Prabhu, Anuja and Mehra, Sarika}
}
