Processi di biorefining per l'estrazione di secondary chemical building blocks da sottoprotti dell'agro-industria
Creators: name: Zanichelli, Dario <1976>
Publisher: name: Alma Mater Studiorum - Università di Bologna
Year: 2008
Subjects: CHIM/11 Chimica e biotecnologia delle fermentazioni

description: Phenol and cresols represent a good example of primary chemical building blocks of which 2.8
million tons are currently produced in Europe each year. Currently, these primary phenolic building
blocks are produced by refining processes from fossil hydrocarbons: 5% of the world-wide
production comes from coal (which contains 0.2% of phenols) through the distillation of the tar
residue after the production of coke, while 95% of current world production of phenol is produced
by the distillation and cracking of crude oil.
In nature phenolic compounds are present in terrestrial higher plants and ferns in several different
chemical structures while they are essentially absent in lower organisms and in animals. Biomass
(which contain 3-8% of phenols) represents a substantial source of secondary chemical building
blocks presently underexploited. These phenolic derivatives are currently used in tens thousand of
tons to produce high cost products such as food additives and flavours (i.e. vanillin), fine chemicals
(i.e. non-steroidal anti-inflammatory drugs such as ibuprofen or flurbiprofen) and polymers (i.e.
poly p-vinylphenol, a photosensitive polymer for electronic and optoelectronic applications).
European agrifood waste represents a low cost abundant raw material (250 millions tons per year)
which does not subtract land use and processing resources from necessary sustainable food
production. The class of phenolic compounds is essentially constituted by simple phenols, phenolic
acids, hydroxycinnamic acid derivatives, flavonoids and lignans. As in the case of coke production,
the removal of the phenolic contents from biomass upgrades also the residual biomass. Focusing on
the phenolic component of agrifood wastes, huge processing and marketing opportunities open
since phenols are used as chemical intermediates for a large number of applications, ranging from
pharmaceuticals, agricultural chemicals, food ingredients etc.
Following this approach we developed a biorefining process to recover the phenolic fraction of
wheat bran based on enzymatic commercial biocatalysts in completely water based process, and
polymeric resins with the aim of substituting secondary chemical building blocks with the same
compounds naturally present in biomass.
We characterized several industrial enzymatic product for their ability to hydrolize the different
molecular features that are present in wheat bran cell walls structures, focusing on the hydrolysis of
polysaccharidic chains and phenolics cross links. This industrial biocatalysts were tested on wheat
bran and the optimized process allowed to liquefy up to the 60 % of the treated matter. The
enzymatic treatment was also able to solubilise up to the 30 % of the alkali extractable ferulic acid.
An extraction process of the phenolic fraction of the hydrolyzed wheat bran based on an
adsorbtion/desorption process on styrene-polyvinyl benzene weak cation-exchange resin Amberlite
IRA 95 was developed. The efficiency of the resin was tested on different model system containing
ferulic acid and the adsorption and desorption working parameters optimized for the crude
enzymatic hydrolyzed wheat bran. The extraction process developed had an overall yield of the
82% and allowed to obtain concentrated extracts containing up to 3000 ppm of ferulic acid.
The crude enzymatic hydrolyzed wheat bran and the concentrated extract were finally used as
substrate in a bioconversion process of ferulic acid into vanillin through resting cells fermentation.
The bioconversion process had a yields in vanillin of 60-70% within 5-6 hours of fermentation.
Our findings are the first step on the way to demonstrating the economical feasibility for the
recovery of biophenols from agrifood wastes through a whole crop approach in a sustainable
biorefining process.