LIME ENERGY CO.
EX-10.1
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<DIV align="center" style="font-size: 10pt; margin-top: 18pt"><IMG src="c48537c4853700.gif" alt="(LIME ENERGY LOGO)">
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<DIV align="right" style="font-size: 10pt; margin-top: 12pt">Exhibit&nbsp;10.1
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<DIV align="left" style="font-size: 10pt; margin-top: 12pt">December&nbsp;30, 2008
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<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Richard P. Kiphart<BR>
William Blair &#038; Co.<BR>
222 W. Adams Street<BR>
Chicago, Illinois 60606

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<DIV align="left" style="font-size: 10pt; margin-top: 12pt">Dear Richard:
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<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Reference is hereby made to the Stock Purchase Agreement, made and entered into as of November
18, 2008 (the &#147;<B>Agreement</B>&#148;), by and among Lime Energy Co. (&#147;<B>Lime</B>&#148;), Richard P. Kiphart individually
and as Sellers&#146; Representative and certain other stockholders of Advanced Biotherapy, Inc. listed
in Schedule&nbsp;A to the Agreement. Capitalized terms used and not otherwise defined herein have the
respective meanings given to such terms in the Agreement.
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<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This letter (the &#147;<B>Extension</B>&#148;) confirms our agreement that the date for the performance of
Lime&#146;s obligation to prepare and file a Registration Statement, pursuant to Section&nbsp;6.15 of the
Agreement, shall be extended to January&nbsp;16, 2009.
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<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Except as specifically modified by this Extension, all other terms and provisions of the
Agreement shall continue in full force and effect.
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<DIV align="left" style="font-size: 10pt; margin-top: 6pt">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Please indicate your agreement by countersigning this letter, in your capacity as Sellers&#146;
Representative pursuant to Section&nbsp;8.4(b) of the Agreement, in the space below and returning an
executed copy via facsimile to Reed Smith, LLP, <U>Attention</U>: Jacob Thride, (312)&nbsp;207-6400.
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<DIV align="left" style="font-size: 10pt; margin-top: 12pt">Sincerely,
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<DIV align="left" style="font-size: 10pt; margin-top: 6pt">/s/ Jeffrey R. Mistarz

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<DIV align="left" style="font-size: 10pt; margin-top: 6pt">Jeffrey R. Mistarz<BR>
Chief Financial Officer<BR>
Lime Energy Co.

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<DIV align="left" style="font-size: 10pt; margin-top: 12pt">ACKNOWLEDGED AND AGREED TO AS OF DECEMBER 31, 2008
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    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">/s/ Richard P. Kiphart
<DIV style="font-size: 1pt; border-top: 1px solid #000000">&nbsp;</DIV>
Richard P. Kiphart
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    <TD valign="top"><DIV style="margin-left:0px; text-indent:-0px">In his capacity as Sellers&#146; Representative</DIV></TD>
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