Enzymes as Biocatalysts for Lipid-based Bioproducts Processing - Food and Industrial Bioproducts and Bioprocessing - page 336

Other parameters of interest in the enzymatic processing of bioactive compounds include
reaction temperature, agitation level and the selection of substrate types and ratio. Firstly,
temperature can influence not only the activation and denaturation of the enzyme, but also
substrate and product solubility and the viscosity of the reaction media (Chebil et al ., 2006 ;
Villeneuve, 2007). Particularly when viscous substrates or ionic liquids are involved, a well
mixed system is very important to ensure proper contact between the biocatalyst and
substrates. From the preceding brief discussion, it is clear that the efficiency of enzymatic
processing of bioactive compounds is affected by a number of parameters. Excellent in-depth
discussions of some key parameters can be found in various reviews (Lau et al ., 2004 ;
Chebil et al ., 2006 ; Villeneuve, 2007 ).
Table 14.3 provides a glimpse of some of the research which has been carried out to
date. One major area of research relates to the enzymatic processing of phenolic acids,
whereby acylation of phenolics, such as dihydrocaffeic, p -hydroxyphenylpropionic,
chlorogenic and ferulic acids, with a range of fatty alcohols have yielded some promising
results (Giuliani et al ., 2001 ; Stamatis et al ., 2001 ; Figueroa-Espinoza and Villeneuve,
2005 ; Duan et al ., 2006). More recently, further studies on ferulic acid have been carried
out using a chemi-enzymatic approach, whereby chemically produced vinyl ferulate was
transesterified with octanol or other compounds, including sterols, for production of
feruloyl derivatives with enhanced antioxidative properties (Chigorimbo-Murefu et al .,
2009). The biosynthesis with octanol was carried out at 45 °C in tert -butyl-methyl ether
using C. antarctica lipase, while C. rugosa lipase was more appropriate for sterol ferulate
biosynthesis due to steric hindrance resulting from both the phenylpropenoic derivatives
and tetracyclic steroid skeleton.
Literature also details acylation reactions of other polyphenolic compounds including
flavonoids. For instance, Stevenson and co-workers (2006) reported biosynthesis reactions
of naringin and isoquercetin with a range of acyl donors, including palmitic, cinnamic and
phenylpropionic acids. In this case, both purified phenolic glycosides and fruit extracts were
investigated in t -butanol at 60 °C for up to seven days, resulting in yields from approxi-
mately 25% to 95%. High purity lauroyl and palmitoyl rutin esters were also prepared
recently by Lue and co-workers (2009) following biosynthesis reactions in acetone at 50 °C
for up to 96 h. Generally, use of increasingly bulky or longer chain length acyl substrates has
often resulted in the need for longer reaction times (Devi et al ., 2008 ).
Enzymatic glucosylation (the addition of a sugar moiety) and amidation (the addition of
an amine moiety) are two additional approaches that can be employed to alter the properties
and functionalities of bioactive compounds (Villeneuve, 2007; Khare et al ., 2009 ). Finally,
many reports also describe approaches involving the enzymatic hydrolysis of various proteins
to yield bioactive peptides with novel antioxidative, antimicrobial and health-promoting
properties (Wei and Chiang, 2009; Zhang et al ., 2009 ).
Generally, enzymatic processing of bioactive compounds can improve the bioactive and
physicochemical properties of a very diverse group of compounds (López-Giraldo et al .,
2009 ; Lue et al ., 2009). However, to do so successfully, it is important to carefully consider
the reaction environment, enzyme stability and the sensitivity of the modified and unmodi-
fied bioactive substrates during optimization of these enzymatic processes. Although an
array of patents exists in the area (Wang et al ., 2008 , Singh and Jagaveerabhadra, 2010 ,
Tashiro et al ., 2010), to date there is little evidence that enzymatic processing of bioactives
is being carried out on a large scale. In reality, cost as well as technical challenges relating
to product separation, enzyme deactivation and the sensitivity of bioactive substrates and
products have limited commercialization of these processes. Nonetheless, demand for