AMENDMENT NO. 1 TO REGISTRATION RIGHTS AGREEMENT

 
THIS AMENDMENT NO. 1 TO REGISTRATION RIGHTS AGREEMENT (“Amendment”) dated as of
July 10, 2008, is entered into among Allegro Biodiesel Corporation, a Delaware
corporation (“Allegro”), Monarch Pointe Fund, Ltd., Mercator Momentum Fund,
L.P., Mercator Momentum Fund III, L.P., M.A.G. Capital, LLC, St. Cloud Partners,
LP, Pentagon Dollar Satellite Fund, and each of the undersigned additional
accredited investors signatories hereto (collectively, the “Holders”).
 
RECITALS
 
WHEREAS, Allegro (formerly known as Diametrics Medical, Inc.) and the Holders
previously entered into a registration rights agreement dated as of September
20, 2006 (the “Agreement”); and
 
WHEREAS, Allegro and the Holders desire to amend Section 2(a) of the Agreement
as provided below, such amendment to be effective as of the date first set forth
above.
 
NOW, THEREFORE, in consideration of the mutual promises, covenants and
agreements set forth herein, and for other good and valuable consideration, the
receipt and sufficiency of which is acknowledged by each of the parties hereto,
the parties agree as follows:
 
1.  Section 2(a) of the Agreement. The last sentence of Section 2(a) of the
Agreement is hereby deleted in its entirety and the following sentence is
substituted therefor:
 
“Once effective, the Company shall use its commercially reasonable efforts to
maintain the effectiveness of the Registration Statement until the earlier of
the date that all of the Registrable Securities have been sold and the first
anniversary of the effective date of the Registration Statement, June 12, 2008
(such date, the “Expiration Date”).”
 
2.  Other Terms and Conditions of Agreement. All other terms and conditions of
the Agreement, to the extent not contradictory to or inconsistent with the
recitals, terms and conditions of this Amendment shall continue to be
applicable. All capitalized terms defined in the Agreement and used herein shall
have the same meaning as set forth in the Agreement unless otherwise defined in
this Amendment.
 
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IN WITNESS WHEREOF, the parties hereto have executed this Amendment as of the
date first above written.

ALLEGRO:
THE HOLDERS:
     
MONARCH POINTE FUND, LTD.
 
By: William Richard Tacon
By: /s/ W. Bruce Comer III              
Its: Liquidator of Monarch Pointe Fund Limited
Name: W. Bruce Comer III                 
Title: Chief Executive Officer              
   
By: /s/ William Tacon                
 
Name: William Tacon
 
Its: Liquidator
     
MERCATOR MOMENTUM FUND, L.P.
 
By: M.A.G. CAPITAL, LLC
 
Its: General Partner
         
By: /s/ David Firestone                
 
Name: David Firestone
 
Its: Managing Member
     
MERCATOR MOMENTUM FUND III, L.P.
 
By: M.A.G. CAPITAL, LLC
 
Its: General Partner
         
By: /s/ David Firestone                
 
Name: David Firestone
 
Its: Managing Member

(Signatures Continued on Next Page)
 
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PENTAGON DOLLAR SATELLITE FUND
         
By: /s/ R. Arliss Francis               
 
Name: R. Arliss Francis
 
Its:  Authorized Signatory for Hamilton Fiduciary Services Limited,
        Corporate Director
     
NAUTILUS TRUST dtd 9/10/99
         
By: /s/ Barry Porter                  
 
Name: Barry Porter
 
Its: Co. Trustee
     
By: /s/ Lea Porter                  
 
Name: Lea Porter
 
Its: Co. Trustee

 
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