need help with some regex

So, I need to DROP the class attribute from the wp_list_categories function, but NOT on the core files.

right now the source code is :

<!--Start krembo99 horiz navigation bar-->
<ul id="menu" class="sf-menu">
<li class="cat-item cat-item-6"><a href="https://www.xxxx.org/wp/?cat=6" title="blabla">Buzziiii</a></li>
<li class="cat-item cat-item-7"><a href="https://www.xxxx.org/wp/?cat=7" title="blabla">Competitionsornot</a>
<ul class='children'>
<li class="cat-item cat-item-14"><a href="https://www.xxxx.org/wp/?cat=14" title="blabla">tesdrtf</a></li>
<li class="cat-item cat-item-13"><a href="https://www.xxxxxx.org/wp/?cat=13" title="blabla">tesr566</a></li></ul></li>
<li class="cat-item cat-item-8"><a href="https://www.xxxxxx.org/wp/?cat=8" title="blabla">Events</a>
</li>
<li class="cat-item cat-item-11"><a href="https://www.xxxxxx.org/wp/?cat=11" title="Vblabla">Featured Articles</a>
</li>
<li class="cat-item cat-item-1"><a href="https://www.xxxxxx.org/wp/?cat=1" title="blabla">Uncategorized</a>
</li>
</ul>
<!--End pages navigation-->

I need to go from this :
<li class="cat-item cat-item-8">
to this :
<li>

So I tried to regex :

<ul id="menu" class="sf-menu"><?php
    $k99_neat_cats = wp_list_categories('orderby=name&amp;show_count=0&amp;title_li=');
    $k99_neat_cats = preg_replace('/\<li class\="(.*?)\"/','',$k99_neat_cats);
    echo $k99_neat_cats;
    ?>
</ul>

no good. any help ???