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

Péter Komáromy,Nándor Nemestóthy,Péter Bakonyi,László Gubicza,Gábor Tóth,Katalin Bélafi-Bakó,Adrienn Kucska

doi:10.3390/fermentation5020031

Abstract

Biological itaconic acid production can by catalyzed by Aspergillus terreus (a filamentous fungi) where the fermentation medium pH is of prominent importance. Therefore, in this work, we investigated what benefits the different pH regulation options might offer in enhancing the process. The batch itaconic acid fermentation data underwent a kinetic analysis and the pH control alternatives were ranked subsequently. It would appear that the pH-shift strategy (initial adjustment of pH to 3 and its maintenance at 2.5 after 48 h) resulted in the most attractive fermentation pattern and could hence be recommended to achieve itaconic acid production with an improved performance using A. terreus from carbohydrate, such as glucose. Under this condition, the itaconic acid titer potential, the maximal itaconic acid (titer) production rate, the length of lag-phase and itaconic acid yield were 87.32 g/L, 0.22 g/L/h, 56.04 h and 0.35 g/g glucose, respectively.

Highlights

Microbial fermentation has been demonstrated as an efficient technology to produce a variety of organic acids such as malic acid, succinic acid, propionic acid, itaconic acid, etc. [1,2,3,4]
It has been argued that besides enabling the appropriate growth of A. terreus [24], such a fermentation environment can be useful for suppressing the formation of by-products that would lower the final itaconic acid yield and productivity [25]
Typical by-products of fungal itaconic acid fermentation can be itatartaric acid, gluconic acid and oxalic acid, depending on the pH conditions, due to mechanisms reviewed by Mondala [10]

Summary

Introduction

Microbial fermentation has been demonstrated as an efficient technology to produce a variety of organic acids such as malic acid, succinic acid, propionic acid, itaconic acid, etc. [1,2,3,4]. The fermentation of itaconic acid can be carried out on numerous feedstocks, including complex agro-industrial wastes such as lignocelluloses as well as simple (monomeric) sugars, e.g., glucose [8]. The properties of the actual starting material will influence the achievable itaconic acid formation efficiency [9,10,11], and besides that, process control via the maintenance of adequate environmental conditions will play a key role. As a matter of fact, ensuring suitable aeration, broth composition, mixing, temperature and pH are crucial criteria for the improved formation of itaconic acid by A. terreus [12,13,14,15]

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Conclusion