Perspectives on Chemicals from Renewable Resources - Sustainable Biotechnology: Sources of Renewable Energy - page 206

Further work is required to realise the potential for further refining which could
lead to the lignocellulosic component being used as a raw material for transportation
fuel and being able to resolve the protein into its constituent amino acids could lead
to application in the chemicals industry (and satisfying the feed market). As impor-
tation of press cakes etc. already takes place at ports, it could be advantageous to
implement the bio-refining there too. For large ports, with large integrated chemical
facilities, such as the port of Rotterdam, this is particularly relevant.
For the use of other (aqueous) rest streams from other industries, such as
Protamylasse R

, it would be advantageous to have further conversions taking place
as close to the original site to prevent the transportation of water. Integration of var-
ious industries (using renewable resources) have already been suggested, such as
that between Dow and Crystalsev.

5.2 Protein Conversion to Amino Acids

In order to be able to utilise proteins as a source of amino acids a number of chal-
lenges need to be overcome. For example once the proteins are isolated they need to
be hydrolysed, but how should this been done? Current practice (for making hydrol-
ysed vegetable proteins) uses 6N hydrogen chloride (HCl) at elevated temperatures
over a prolonged period of time. Amongst other things this leads to degradation
of a number of (valuable) amino acids. As well as this, a copious amount of base
is required to neutralise the solution. While the costs of HCl (and NaOH) are rela-
tively low and production of technical grade HCl is often a result of the chloronation
of hydrocarbons (such as in the synthesis of vinyl chloride in PVC production), the
production of large amounts of inorganic salt is undesirable. They must be separated
from the amino acid mixture as it may disrupt potential separation processes such as
ion exchange (IE) or electrodialysis (ED), reducing the efficiency and increasing the
costs of obtaining the desired (amino acid) end product. Thus alternative methods of
hydrolysing the protein are required. One option to hydrolyse proteins and reduce
salt (by-product) formation could be the (partial) use of enzymes such as proteases
(although some salt may be produced to pH maintenance). Proteases are used in a
number of applications in the food and beverages industry. The degree of hydrol-
ysis, although not complete, can be quite high (up to 90%) [45] but does require
high dosages and a cocktail of various proteases (with varying specificity) in order
to achieve this. Due to this the costs are prohibitive for large scale, bulk chemical
production applications.

5.3 Amino Acid Separation

The hydrolysed medium contains a mixture of amino acids which require separa-
tion in order that they can be used for their particular application. As previously
described, the uses of IE and ED have been widely reported in the literature as