Optimized pH and Its Control Strategy Lead to Enhanced Itaconic Acid Fermentation by Aspergillus terreus on Glucose Substrate

An Eclectic Review on Dicarboxylic Acid Production Through Yeast Cell Factories and Its Industrial Prominence

Dicarboxylic acid (DCA) is a multifaceted chemical intermediate, recoursed to produce many industrially important products such as adhesives, plasticizers, lubricants, polymers, etc. To bypass the shortcomings of the chemical methods of synthesis of DCA and to reduce fossil fuel footprints, bio-based synthesis is gaining attention. In pursuit of an eco-friendly sustainable alternative method of DCA production, microbial cell factories, and renewable organic resources are gaining popularity. Among the plethora of microbial communities, yeast is being favored industrially compared to bacterial fermentation due to its hyperosmotic and low pH tolerance and flexibility for gene manipulations. By application of rapidly evolving genetic manipulation techniques, the bio-based DCA production could be made more precise and economical. To bridge the gap between supply and demand of DCA, many strategies are employed to improve the fermentation. This review briefly outlines the advancements in DCA production using yeast cell factories with the exemplification of strain improvement strategies.

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.

Sustainable Downstream Separation of Itaconic Acid Using Carbon-Based Adsorbents

Separation of itaconic acid from aqueous solution has been explored using various carbon-based adsorbents obtained from the pyrolysis and KOH activation of coconut shell biomass. The best preparation conditions to obtain a tailored adsorbent for itaconic acid purification were identified via a Taguchi experimental design, where its adsorption properties were maximized. The best activated carbon was obtained via coconut shell pyrolysis at 750 °C for 4 h plus an activation with 0.1 KOH and a final treatment at 800 °C for 2 h. This adsorbent showed an adsorption capacity of 4.31 mmol/g at 20 °C and pH 3 with a surface area of 466 m2/g. Itaconic acid separation was exothermic and pH-dependent where electrostatic forces and hydrogen bonding were the main adsorption interactions. Calculated adsorption rate constants for itaconic acid adsorption were 0.44–1.20 h-1. Results of adsorbent characterization analysis indicated the presence of a crystallization of itaconic acid molecules onto the activated carbon surface where 3–4 molecules could interact to form the clusters. This organic acid was recovered from the adsorbent surface via desorption with water or ethanol, thus facilitating its final purification. The best activated carbon obtained in this study is a promising alternative to perform sustainable and energy-efficient downstream separation and purification of itaconic acid produced via fermentation.

Investigation of Itaconic Acid Separation by Operating a Commercialized Electrodialysis Unit with Bipolar Membranes

Nowadays, the merging of membrane and fermentation technologies is receiving significant attention such as in the case of itaconic acid (IA) production, which is considered as a value-added chemical. Its biotechnological production is already industrially established; however, the improvements of its fermentative and recovery steps remain topics of significant interest due to sustainable development trends. With an adequate downstream process, the total price of IA production can be reduced. For the task of IA recovery, a contemporary electro-membrane separation processes, electrodialysis with bipolar membranes (EDBM), was proposed and employed in this work. In the experiments, the laboratory-scale, commercialized EDBM unit (P EDR-Z/4x) was operated to separate IA from various model solutions compromised of IA (5–33 g/L), glucose (varied in 15–33 g/L as a residual substrate during IA fermentation) and malic acid (varied in 0–1 g/L as a realistic by-product of IA fermentation) under different initial pH (2–5) and applied potential conditions (10–30 V). Unambiguously negative effects related to the glucose and malic acid as impurities were found neither on the IA recovery ratio nor on the current efficiency, falling into the ranges of 90–97% and 74.3–98.5%, respectively. The highest IA recovery ratios of 97% and 98.5% of current efficiency were obtained with the model fermentation solution containing 33 g/L IA, 33 g/L glucose at 20 V and an initial pH of 5. However, the selective separation of IA needs further investigations with a real fermentation broth, and the findings of this research may contribute to further studies in this field.

Continuous Flow Upgrading of Selected C2-C6 Platform Chemicals Derived from Biomass

The ever increasing industrial production of commodity and specialty chemicals inexorably depletes the finite primary fossil resources available on Earth. The forecast of population growth over the next 3 decades is a very strong incentive for the identification of alternative primary resources other than petro-based ones. In contrast with fossil resources, renewable biomass is a virtually inexhaustible reservoir of chemical building blocks. Shifting the current industrial paradigm from almost exclusively petro-based resources to alternative bio-based raw materials requires more than vibrant political messages; it requires a profound revision of the concepts and technologies on which industrial chemical processes rely. Only a small fraction of molecules extracted from biomass bears significant chemical and commercial potentials to be considered as ubiquitous chemical platforms upon which a new, bio-based industry can thrive. Owing to its inherent assets in terms of unique process experience, scalability, and reduced environmental footprint, flow chemistry arguably has a major role to play in this context. This review covers a selection of C₂ to C₆ bio-based chemical platforms with existing commercial markets including polyols (ethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerol, 1,4-butanediol, xylitol, and sorbitol), furanoids (furfural and 5-hydroxymethylfurfural) and carboxylic acids (lactic acid, succinic acid, fumaric acid, malic acid, itaconic acid, and levulinic acid). The aim of this review is to illustrate the various aspects of upgrading bio-based platform molecules toward commodity or specialty chemicals using new process concepts that fall under the umbrella of continuous flow technology and that could change the future perspectives of biorefineries.

Modern Technologies and Their Influence in Fermentation Quality

Since the beginning of enology and fermentation research, wine quality has been parametrized from a chemical and sensory point of view [...]

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.