The correct answer is (4) Mammalian cell line.

Why mammalian cell lines are required

Mammalian cells (e.g., CHO, HEK293) possess the endoplasmic reticulum and Golgi glycosylation machinery needed for complex N‑linked and O‑linked glycosylation of secreted and membrane proteins. They can add and process sugar chains in patterns similar to those in humans, which is essential for many therapeutic proteins (antibodies, hormones, cytokines) to be stable and functional.

Thus, for recombinant peptides/proteins that must be glycosylated, a mammalian cell line (option 4) is the appropriate system.

Why bacterial systems are unsuitable

Options (1), (2), and (3) differ only in scale or naming of bacterial culture systems:

• Large bacterial fermenters

• Small bacterial fermenters

• Normal bacterial bioreactors

Escherichia coli and most standard bacteria lack the eukaryotic glycosylation pathways; they do not perform complex N‑ or O‑linked glycosylation, regardless of fermenter size or configuration. Even though bacteria are excellent for producing large amounts of non‑glycosylated proteins, they cannot correctly glycosylate eukaryotic peptides without extensive engineering, which is not implied here.

Therefore, among the given choices, only mammalian cell lines reliably provide the required post‑translational glycosylation for recombinant peptides.