Evaluating the potential of semi-continuous itaconic acid fermentation by Aspergillus terreus: operational profile and experiences.

Itaconic acid is an important bio-based chemical. The present study aims to evaluate the applicability of semi-continuous fermentation technique for itaconic acid production by Aspergillus terreus. The fermentation is planned to be connected with bipolar membrane electrodialysis unit for acid recovery. This process allows the reuse of residual glucose from the effluent. Our particular attention was focused on the effect of glucose concentration. Two different glucose supplementation strategies were tested: constant glucose concentration in the refilling medium and adjusted glucose concentration in order to maintain a continuously high - 120 g/L - glucose concentration in the fermentor. The itaconic acid titre, yield and productivity for the 24 h time periods between draining/refilling interventions were investigated. The constantly high glucose concentration in the fermentor resulted in doubled biomass formation. The average itaconic acid titre was 32.9 ± 2.7 g/L. The producing strain formed numerous spores during semi-continuous fermentation that germinated continuously. Yield and volumetric productivity showed a periodic pattern during the procedure.

Evaluating aeration and stirring effects to improve itaconic acid production from glucose using Aspergillus terreus.

The effects of the bioreactor conditions, in particular the mode and intensity of aeration and mixing were studied on itaconic acid (IA) fermentation efficiency by Aspergillus terreus strain from glucose substrate. IA was produced in batch system by systematically varying the oxygen content of the aeration gas (from 21 to 31.5 vol% O2) and the stirring rate (from 150 to 600 rpm). The data were analyzed kinetically to characterize the behavior of the process, and besides, the performances were evaluated comparatively with the literature. It turned out that the operation of the bioreactor with either the higher inlet O2 concentration (31.5 vol% O2) or faster stirring (600 rpm) could enhance biological IA generation the most, resulting in yield and volumetric productivity of 0.31 g IA/g glucose and 0.32 g IA/g glucose and 3.15 g IA/L day and 4.26 g IA/L day, respectively. Overall, the significance of fermentation settings was shown in this work regarding IA production catalyzed by A. terreus and notable advances could be realized by adjusting the aeration and stirring towards an optimal combination.

Isolation and some effects of functional, low-phenylalanine kappa-casein expressed in the milk of transgenic rabbits.

Patients suffering certain metabolic diseases (e.g. phenylketonuria) need a low-phenylalanine diet throughout their lives. Transgenic rabbits were created to express low-phenylalanine kappa-casein in their milk. The aim was to demonstrate for the first time the feasibility of producing a modified milk protein in addition to normal milk proteins. A gene construct containing the coding region of the rabbit kappa-casein gene was modified by site-specific oligonucleotide directed mutagenesis. Four of the five phenylalanine amino acids present in the mature protein were mutated and the gene construct was used to create two transgenic rabbit lines. The transgenic rabbits produced the recombinant kappa-casein at a high level in their milk causing a reduction in the average size of the casein micelles. The low-phenylalanine kappa-casein was digestible with chymosin and it was separated from its native counterpart and from the other milk proteins by a one-step HPLC method on a reversed-phase column. In the future, low-phenylalanine casein produced in transgenic animals could be used as dietary replacements to meet the special requirements of certain consumer groups.