How to customize words in blog title separately

Hi,

I am working on a blog site, and I am using the WordPress Loop in order to parse the Blog’s title on the webpage using the following code in the header.php file :

<div class="site-branding">
  <h1 class="site-title"><a href="<?php echo esc_url( home_url( '/' ) ); ?>"      rel="home"><?php bloginfo( 'name' ); ?></a></h1>
  <h2 class="site-description"><?php bloginfo( 'description' ); ?></h2>
</div><!-- .site-branding -->

I want to add a <span> tag around 1 word of the title (not the description), and style it separately using CSS. How would this be possible?

Thanks in advance!