SOC is an 'optimal medium' aimed at providing all nutrients and additives that may help cells recover after heat shock. It is true that the recovery step may not be essential on all occassions, but it likely that using SOC will improve the transformation efficiency and may be critical in certain instances.

The reason SOC (or other super optimal media) are used in commercial kits is that using this will improve the chances of success...as to whether it is actually necessary, that depends on on a whole host of contributing factors (see atricle below for more info) Article Studies on transformation of Escherichia coli with plasmids

So, to answer your question as to if it is necessary - sometimes it is and sometimes it isn't. I know that sounds like a cop out, but it is the case.

All the best

Barry

I used several protocol and I did not observe any different between recovery with SOC or LB, while transforming with miniprep-purified plasmids.

Recovery is better with LB than plating the cells directly after heat shock. However while using Top10 or other non expressing cells, the number of clones is so high than I think recovery with LB is optional. It seems to be necessary while transforming with a ligation product (which may be improved by SOC but it worked with LB for me).

Maybe you can think about using SOC if your clones are difficult to obtain, or if the antibiotic used is particularly toxic (and not bacteriostatic) ?

SOC is not mandatory, Instead you can also use LB broth. Transformation is depends on handling, heating-cooling and quantified DNA.

To use LB broth in place of SOC, how can we prepare the LB broth medium? and how much LB medium we should use?

Actually, for plasmids with ampicillin selection marker, it can even skip the procedure of recovery.

1 ml LB is ok for recovery.