Kinetics of gluconic acid production and cell growth in a batch bioreactor by Aspergillus niger using breadfruit hydrolysate

Abstract

The kinetics of gluconic acid production by Aspergillus niger (A. niger) using breadfruit hydrolysate was studied in a batch bioreactor. A simple model of Luedeking-Piret, logistic, and Luedeking-Piret-like equations were proposed for gluconic acid production, cell growth, and breadfruit hydrolysate consumption respectively. The maximum gluconic acid concentration (Pt) of 109.95 g/L with 0.967 g/g process yield (88.70%) was obtained for the medium containing 120 g/l breadfruit hydrolysate at 2 vvm aeration rate. For the same conditions, the biomass concentration and maximum specific growth were obtained as 24.3 g/L and 0.018 hr 21 respectively. The models proposed for the gluconic acid production was sufficiently satisfactory, since the theoretical values of Pt (100.94 g/L) and biomass concentration (23.43 g/L) obtained from the models were almost the same with the experimental values. The model for the breadfruit hydrolysate utilization gave R 2 and Adj. R 2 of above 0.840 and 0.660 respectively; an indication that the model is suitable for the production of gluconic acid. Therefore, the concentration of initial breadfruit hydrolysate as substrate and aeration rate have shown significant effect on gluconic acid production and A. niger accumulation. The evaluation of the models showed that the gluconic acid production was growth-associated. Practical applicationsBreadfruits, a perishable fruit has been abundantly found in Ile-Ife, Nigeria where 50% of it perishes due to its short shelf-life. This study therefore provides alternative use for breadfruit, in order to reduce its wastage. Furthermore, the growing demand of gluconic acid can be met through the use of this cheap and available breadfruit. The findings in this study can be employed to develop a bioreactor for fermentation of breadfruit hydrolysate to produce gluconic acid. K E Y W O R D SAspergillus niger, breadfruit, fermentation, gluconic acid, hydrolysis

Enhancement of gluconic acid production by Aspergillus niger from by‐products as glucose source using pressurized air conditions

“…For example, during the production of GA by A. niger from molasses, in a 4 L stirred tank bioreactor, the dissolved oxygen decreased quickly to 36% of saturation after 3 h of cultivation 15 . Increasing oxygen supply at the expense of high agitation and aeration rates led to an enhancement of gluconic acid production by A. niger from corn stover hydrolysate 33 and breadfruit hydrolysate 34 . The use of pure oxygen 35 and oxygen‐enriched air 6,36 has also been attempted to circumvent the oxygen limitation in A. niger cultures and improve GA productivity, but these approaches are not economically viable at industrial scale and require special handling.…”

“…15 Increasing oxygen supply at the expense of high agitation and aeration rates led to an enhancement of gluconic acid production by A. niger from corn stover hydrolysate 33 and breadfruit hydrolysate. 34 The use of pure oxygen 35 and oxygenenriched air 6,36 has also been attempted to circumvent the oxygen limitation in A. niger cultures and improve GA productivity, but these approaches are not economically viable at industrial scale and require special handling. The application of pressurized air to A. niger 37,38 and Aureobasidium pullulans 8 cultures for GA biosynthesis was previously studied in pure glucose media and the results were as promising as those obtained in the present work.…”

Lactic acid production: Utilization of yam peel hydrolysate as a substrate using Rhizopus orysae in kinetic studies

“…A logistic kinetic model that stimulates growth was suggested by Mitra and Dutta 47 and was adopted to determine the biomass growth ( R. oryzae ) in this study. According to Ajala et al ., 48 the model is characterized by the biomass growth inhibition, independent of substrate and product, which is a common phenomenon encountered in batch culture. The model is thus expressed as Eqn (4): Integrating Eqn (4) and using the boundary condition of X (0) = X o produced Eqn (5): …”

“…The substrate (YPH/SGS) utilization for the LA production using Rhizopus oryzae in fermentation processes of the surface and submerged were also evaluated in a kinetic study. A modified model of Luedeking–Piret that neglects the amount of YPH/SGS utilized for the LA formation according to Ajala et al 48 . and Pazouki et al 49 .…”

“…Apart from the aforementioned kinetics parameters analyzed, other kinetics coefficients that explain the efficiency of the fermentation process of LA production were also evaluated using the mathematical expressions defined by Žunar et al ., 52 Germec et al 31 . and Ajala et al 48 . as shown in Eqns (12) and (13): where; Y P / S = Product yield coefficient (g g −1 );…”