You can also use AWK which can give you more flexibility to handle the file
awk '{ print "chmod 755 "$0"" | "/bin/sh"}' file.txt
if your file has a field separator like:
field1,field2,field3
To get only the first field you do
awk -F, '{ print "chmod 755 "$1"" | "/bin/sh"}' file.txt
You can check more details on GNU Documentation https://www.gnu.org/software/gawk/manual/html_node/Very-Simple.html#Very-Simple