Aeration and yeast extract requirements for kojic acid production by Aspergillus flavus link

Abstract

Growth and kojic acid production by Aspergillus flavus Link 44-1 were studied at different levels of dissolved oxygen tension (DOT) using a 2-l stirred tank fermenter. In all experiments, agitation was fixed at 600 rpm and DOT was controlled at different levels by varying airflow rates. Single-phase DOT control at three different levels (30, 50, and 80% saturation) did not enhance kojic acid production when compared to fermentation without DOT control (13.5 g l-l). The production of kojic acid in a fermentation with single-phase DOT control at 80% was comparable to that of a fermentation without DOT control. Decreased DOT levels below 80% reduced the production of kojic acid significantly although the biomass increased. When DOT was controlled at a very high level (80%) during active growth and then decreased to a low level (30%) during the production phase (i.e., two-phase DOT control), the production of kojic acid (28.9 g l-l) was increased by about two times compared to a fermentation without DOT control; however, when yeast extract was added continuously in a fermentation with two-phase DOT control, active growth occurred during the production phase and the maximum accumulation of kojic acid was reduced significantly. High DOT during on active growth phase and no addition of yeast extract during the production phase were required to enhance kojic acid biosynthesis. The most effective control strategy for kojic acid production, therefore, was to control DOT at very high levels during active growth and not add a nitrogen source during the production phase while using low levels of DOT.

An In vitro Approach for Evaluating Antimicrobial Activity and Production of Kojic Acid by Aspergillus flavus Isolated from Karwar Region

“…Hence ample amount of kojic acid and dry mass were obtained with ethyl acetate extract as the fermentation process progressed up to 13days. Such type of performance of kojic acid biosynthesis and dry mass by A.flavus was reported [50][51][52][53][54][55][56] .…”

Influence of pH on Kojic Acid Fermentation by Aspergillus flavus

“…The initial pH of the culture was adjusted to 3 and the culture pH was controlled at pH 3 during the production phase by the automatic addition of either 0.2 N HCl or 0.2 N NaOH. The optimum aeration control strategy for maximum batch production of kojic acid was employed (Ariff et al, 1996). In this aeration control strategy, DOT during active growth phase was controlled at 80% saturation and then switched to 30% saturation during the production phase.…”

“…Good performance of kojic acid production was also obtained by immobilized cell of A. oryzae at pH 3 ( Kwak and Rhee, 1992). Kojic acid fermentation can be divided into two phases; growth phase and production phase (Ariff et al, 1996). During growth phase, enzymes relevant to kojic acid metabolic pathway were produced and kojic acid is synthesized by the direct conversion from glucose through the multistep reactions of these enzymes without any cleavage into small fragments (Arnstein and Bentley, 1953).…”

“…During growth phase, enzymes relevant to kojic acid metabolic pathway were produced and kojic acid is synthesized by the direct conversion from glucose through the multistep reactions of these enzymes without any cleavage into small fragments (Arnstein and Bentley, 1953). The cell bound enzymes system involved in kojic acid biosynthetic pathway was very stable when the cells were resuspended in buffered glucose solution (Ariff et al, 1996;Bajpai et al, 1982). There must be an optimum culture pH for growth of kojic acid-producing fungus and enhancement of secretion of the enzymes responsible for kojic acid synthesis and also an optimum solution pH for the activities and stability of these enzymes.…”

Effects of dual impeller system of Rushton turbine, concave disk turbine and their combinations on the performance of kojic acid fermentation by Aspergillus flavus Link 44‐1

“…Industrially, kojic acid is produced via submerged fermentation in stirred tank bioreactor. A number of issues related to the strain and process development for kojic acid fermentation in stirred tank bioreactor have been addressed and reported . However, new knowledge and information are progressively needed for further improvement of large scale kojic acid production.…”