EXHIBIT 31 (a)

CERTIFICATIONS

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|In connection with the
 Annual Report on Form 10-K of Enzo Biochem, Inc. (the Company) for the
 fiscal year ended July 31, 2011 as filed with the Securities and Exchange
 Commission on the date hereof, I, Elazar Rabbani, Ph.D., Chief Executive
 Officer of the Company, certify, pursuant to 18 U.S.C. § 1350, as adopted
 pursuant to § 302 of the Sarbanes-Oxley Act of 2002, that:
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|1.                                                                                                                                                                                                                                                                                                                                                                                           | I have reviewed this Annual
 Report on Form 10-K of Enzo Biochem, Inc.                                                                                                                                                                                                                                                                 
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|2.                                                                                                                                                                                                                                                                                                                                                                                           | Based on my knowledge, this
 report does not contain any untrue statement of a material fact or omit to
 state a material fact necessary to make the statements made, in light of the
 circumstances under which such statements were made, not misleading with
 respect to the period covered by this report;                         
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|3.                                                                                                                                                                                                                                                                                                                                                                                           | Based on my knowledge, the
 financial statements, and other financial information included in this
 report, fairly present in all material respects the financial condition,
 results of operations and cash flows of the Company as of, and for, the
 periods presented in this report;                                               
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|4.                                                                                                                                                                                                                                                                                                                                                                                           | The Companys other
 certifying officer and I are responsible for establishing and maintaining
 disclosure controls and procedures (as defined in Exchange Act Rules 13a 
 15(e) and 15d  15(e)) and internal control over financial reporting (as
 defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the Company and
 have:
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|                                                                                                                                                                                                                                                                                                                                                                                             | (a)                                                                                                                                                                                                                                                                                                                                     | Designed such disclosure
 controls and procedures, or caused such disclosure controls and procedures to
 be designed under our supervision, to ensure that material information
 relating to the Company, including its consolidated subsidiaries, is made
 known to us by others within those entities, particularly during the period
 in which this report is being prepared;
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|                                                                                                                                                                                                                                                                                                                                                                                             | (b)                                                                                                                                                                                                                                                                                                                                     | Designed such internal
 control over financial reporting, or caused such internal control over
 financial reporting to be designed under our supervision, to provide
 reasonable assurance regarding the reliability of financial reporting and the
 preparation of financial statements for external purposes in accordance with
 generally accepted accounting principles;    
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|                                                                                                                                                                                                                                                                                                                                                                                             | (c)                                                                                                                                                                                                                                                                                                                                     | Evaluated the effectiveness
 of the Companys disclosure controls and procedures and presented in this report
 our conclusions about the effectiveness of the disclosure controls and
 procedures, as of the end of the period covered by this report based on such
 evaluation; and                                                                                            
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|                                                                                                                                                                                                                                                                                                                                                                                             | (d)                                                                                                                                                                                                                                                                                                                                     | Disclosed in this report
 any change in the Companys internal control over financial reporting that
 occurred during the Companys most recent fiscal quarter (the Companys
 fourth fiscal quarter in the case of an annual report) that has materially
 affected, or is reasonably likely to materially affect, the Companys
 internal control over financial reporting; and
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|5.                                                                                                                                                                                                                                                                                                                                                                                           | The Companys other
 certifying officer and I have disclosed, based on our most recent evaluation
 of internal control over financial reporting, to the Companys auditors and
 the audit committee of the Companys board of directors (or persons
 performing the equivalent functions):                                             
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|                                                                                                                                                                                                                                                                                                                                                                                             | (a)                                                                                                                                                                                                                                                                                                                                     | All significant
 deficiencies and material weaknesses in the design or operation of internal
 control over financial reporting which are reasonably likely to adversely
 affect the Companys ability to record, process, summarize and report
 financial information; and                                                                                                      
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|                                                                                                                                                                                                                                                                                                                                                                                             | (b)                                                                                                                                                                                                                                                                                                                                     | Any fraud, whether or not
 material, that involves management or other employees who have a significant
 role in the Companys internal control over financial reporting.                                                                                                                                                                                                       

Date: October 14, 2011

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| | By: | /s/ Elazar Rabbani, Ph.D.
| |     |                          
| |     | Elazar Rabbani, Ph.D.    
| |     | Chief Executive Officer  

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