Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of stock-based compensation expense

Stock-based compensation expense is included in the consolidated statements of operations as follows (in thousands):

	Three Months Ended March 31,
	2015		2014
Research and development (1)	$	291	$	239
Selling, general and administrative	994		990
Total	$	1,285	$	1,229

(1) Stock-based compensation expense associated with cost of biocatalyst product sales is included in research and development. Amounts were immaterial for all periods presented.

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity

The following table presents total stock-based compensation expense by security types included in the condensed consolidated statements of operations for the three months ended March 31, 2015 and 2014 (in thousands):

	Three Months Ended March 31,
	2015		2014
Stock options	$	248	$	276
RSUs and RSAs	792		869
PSUs	245		84
Total	$	1,285	$	1,229

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The ranges of weighted-average assumptions used to estimate the fair value of employee stock options granted were as follows:

	Three months ended March 31,
	2015			2014
Expected term (in years)	6.0			6.0
Volatility	66		%	64		%
Risk-free interest rate	1.69		%	1.90		%
Dividend yield	—		%	—		%
Weighted-average estimated fair value of stock options granted	$	2.05		$	1.15