Aspergillus examples

To develop a continuous process, the immobilisation of aminoacylase of Aspergillus oryzae by a variety of methods was studied, for example ionic binding to DEAE-Sephadex, covalent binding to iodo-acetyl cellulose and entrapment in polyacrylamide gel. Ionic binding to DEAE-Sephadex was chosen because the method of preparation was easy, activity was high and stable, and regeneration was possible. 

In all the reported examples, the enzyme selectivity was affected by the solvent used, but the stereochemical preference remained the same. However, in some specific cases it was found that it was also possible to invert the hydrolases enantioselectivity. The first report was again from iQibanov s group, which described the transesterification of the model compound (13) with n-propanol. As shown in Table 1.6, the enantiopreference of an Aspergillus oryzae protease shifted from the (l)- to the (D)-enantiomer by moving from acetonitrile to CCI4 [30]. Similar observations on the inversion of enantioselectivity by switching from one solvent to another were later reported by other authors [31]. 

Biocatalysis has emerged as an important tool for the enantioselective synthesis of chiral pharmaceutical intermediates and several review articles have been published in recent years [133-137]. For example, quinuclidinol is a common pharmacophore of neuromodulators acting on muscarinic receptors (Figure 6.50). (JJ)-Quinudidin-3-ol was prepared via Aspergillus melleus protease-mediated enantioselective hydrolysis of the racemic butyrate [54,138]. Calcium hydroxide served as a scavenger of butyric acid to prevent enzyme inhibition and the unwanted (R) enantiomer was racemized over Raney Co under hydrogen for recycling. 

For example, Candida albicans and (especially) Aspergillus niger are much more resistant to a variety of biocides than Gram-positive and Gram-negative bacteria. 

An alternative to extraction crystallization is used to obtain a desired enantiomer after asymmetric hydrolysis by Evonik Industries. In such a way, L-amino acids for infusion solutions or as intermediates for pharmaceuticals are prepared [35,36]. For example, non-proteinogenic amino acids like L-norvaline or L-norleucine are possible products. The racemic A-acteyl-amino acid is converted by acylase 1 from Aspergillus oryzae to yield the enantiopure L-amino acid, acetic acid and the unconverted substrate (Figure 4.7). The product recovery is achieved by crystallization, benefiting from the low solubility of the product. The product mixture is filtrated by an ultrafiltration membrane and the unconverted acetyl-amino acid is reracemized in a subsequent step. The product yield is 80% and the enantiomeric excess 99.5%. 

As discussed above, wheat has been used only rarely for molecular farming. Thus far, the only example of a pharmaceutical protein produced in wheat is a single chain Fv antibody, which was expressed using the Ubil promoter and achieved a maximum expression level of 1.5 pg g 1 dry weight [77]. Transgenic wheat producing Aspergillus phytase has also been reported [78]. 

Following Mosher s report, several publications appeared showing the preparation of Mosher s acid. One example is the chemoenzymatic preparation of Mosher s acid using Aspergillus oryzae protease (Scheme 1-5)24 ... 

Finally, there are some examples for reduction of various compounds, which are of biochemical interest. Racemic abscisic acid was reduced with Aspergillus niger affording (—)-(l/5 ,2// )-2/,3/-dihydroabscisic acid with >95% ee (equation 43)117. 

Soil populations and aflatoxin contamination are influenced by weather patterns, with hot dry soils favoring the Aspergillus section Flavi. In terms of geographic location, A. flavus incidence is correlated with high minimum temperatures and inversely correlated to latitude. For example, corn ears that develop at temperatures of 28 to 32°C are far more likely to be contaminated by aflatoxin than ears grown later in the season at lower temperatures. However, late planting is not economically feasible due to lower crop yields. Besides hot dry weather, the level of insect and rodent activity in an area may also substantially favor colonization and aflatoxin production. Plant fertility, density, and disease also play roles in the level of aflatoxin contamination. 

---