Using 'if' within a 'while' loop in Bash

You should be checking for >, not <, no?

while read line; do
    if [[ $line =~ ">" ]]; then
        echo $line
    fi
done < /tmp/voo

Do you really need regex here? The following shell glob can also work:

while read line; do [[ "$line" == ">"* ]] && echo "$line"; done < /tmp/voo

OR use AWK:

awk '/^>/ { print "processing: " $0 }' /tmp/voo