Preparation of basal differentiation media

BE1a medium	Final concentration	Amount
MCDB131	n/a	500 mL
Fatty-acid-free BSA	0.1%	0.5 g
Sodium bicarbonate	1.174 g/L	587 mg
Glucose	0.8 g/L	400 mg
L-Glutamine	2 mM	5 mL
Total	n/a	505 mL

After preparation of the media, mix on a magnetic stirrer until everything is completely dissolved (at least 20 min). Filter the solution through a 0.22 μm filter and collect it in a sterile glass bottle. We recommend preparing 50 mL aliquots and store in the dark at 4°C for up to 4 weeks.