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MIG1, encoding a C2H2 zinc-finger repressor protein implicated in carbon catabolite repression, was discovered to be involved in non-sexual flocculation of Saccharomyces cerevisiae. Disruption of MIG1 in a flocculent mutant strain of NCYC 227, produced a non-flocculent phenotype. Expression of MIG1 on a 2 micro pRS426 vector in a non-flocculent strain, YM 4134, caused flocculation. MIG1 on a high-copy-number LEU2-d plasmid caused intense flocculation in the same strain. Mutations in the SSN6 and TUP1 genes confer a flocculent phenotype in non-flocculent strains of S. cerevisiae.

Non-sexual flocculation of the yeast Saccharomyces cerevisiae NCYC 227 strains involves a 13 kDa cell-wall-surface protein bound to mannose. The proteins binds in mannose in the presence of calcium and forms aggregates. Flocculation of the yeast cells occurring due to hydrogen bonding between the protein and mannan indicates protein aggregation inhibition at high temperatures and the urea content.

A techno-economic analysis of submerged (SmF) and solid state fermentation (SSF) processes for Aspergillus carbonarius polygalacturonase production was performed to make an appropriate process selection. The downstream processing involved integrated membrane process (IMP) and alginate affinity precipitation (AAP). For a production scale of 30kL purified polygalacturonase concentrate per year, the total upstream cost of SmF was 14% lower than the SSF process. Downstream processing cost by IMP was 47% lower than AAP. The SmF-IMP process required a total capital investment that was 15-24% lower than the SmF-AAP and SSF-AAP processes. The corresponding unitary product cost was also lower by 24-36% in SmF-IMP process. Thus the SmF-IMP process proved to be very attractive from an economic point of view., (Copyright © 2012 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.)

Purification of polygalacturonase (PG) from the cultures of Aspergillus carbonarius obtained by acetate buffer extraction after solid-state fermentation was attempted by integrated membrane process and alginate affinity precipitation. The carbohydrates were completely eliminated (98%-99%) with a PG recovery of 72%-80% during integrated membrane process, which would otherwise interfere with the purification process and lead to enzyme loss. However, specific activity of PG did not improve (1.19-1.21 fold) due to the presence of other similar molecular mass proteins. Under optimum conditions of affinity precipitation, the specific activity of PG enhanced to 2450 U/mg (4 fold) with almost complete elimination of carbohydrates and colour compounds resulting in a PG recovery of 61%. PG purity obtained with ultrafiltration (UF) was comparable with the conventional dialysis during desalting eluted PG, besides UF rendered a concentrated PG. The enzyme purity stated was as descend by SDS-PAGE. The results suggested suitability of affinity precipitation for PG purification from solid-state cultures and the potential of UF as a single step process for handling eluted PG., (Copyright (c) 2009 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.)

A mutant Aspergillus carbonarius selected for temperature tolerance after UV treatment, when grown in shake flasks, produced mycelia bearing yellow pigment. Since the mutant was affected in sterol biosynthetic pathway, the pigment was apparently produced to maintain membrane fluidity and rigidity for growth sustenance in low-pH culture broth. Nuclear magnetic resonance analyses characterizing the pigment as a partially saturated canthaxanthin, containing beta-ionone end rings, suggested its application as a retinoid. When tested for this property in retinoic acid receptor expressing prostate cancer cell line, LNCaP, the fungal partially saturated canthaxanthin induced apoptosis. Low apoptosis percentage in DU145 prostrate cancer cells that does not express functional retinoic acid receptor-beta (RAR-beta) suggested binding specificity of the partially saturated canthaxanthin for RAR-beta.