A Standard Inoculum for Citric Acid Production in Submerged Culture

Abstract

A standard vegetative inoculum of Aspergillus niger has been developed for the submerged citric acid fermentation of sugar beet molasses. Increasing the ferrocyanide content and the pH of the seed mash, within limits, decreased the rate of development of the mold pellets whereas increasing the spore inoculum increased the rate of development. Using this "standard" inoculum, an average yield of 8.9% anhydrous citric acid (68.5% conversion of available sugar) was obtained in 116 hr. The standard deviation between runs was 4.5% of the mean citric acid yield. An abrupt breakdown of the fermentation process decreased the yield by 50% and increased the standard deviation to 28.5% of the mean yield. The breakdown was overcome by changing the sporulation medium from a chemically-defined synthetic type to a nutritionally-richer type. Results indicate that serial transfer on a synthetic medium weakened the culture and made the fermentation unstable.

Study of pellet formation of filamentous fungi Rhizopus oryzae using a multiple logistic regression model

“…It has been reported that different strains have different response to pH value (Metz et al, 1977). For this particular strain of R. oryzae, the results show that there were no significant differences on pellet formation with a pH range of 2.5-7, which means that this strain is relatively tolerant to pH compared to some other fungal strains such as A. niger and P. chrysogenum (Galbraith and Smith, 1969;Pirt and Callow, 1959;Steel et al, 1954). However, neutralizer is still needed to prevent pH from dropping into the low pH range of 2-3 which is not favorable for biomass accumulation (Znidarsic et al, 1998).…”

“…Filamentous fungal fermentation is widely used to commercially produce useful products such as organic acids, enzymes, antibiotics, and cholesterol lowering drugs (Statins) (Cao et al, 1996;Casas Lopez et al, 2004;Chahal, 1985;Hang, 1989;Papagianni, 2004;Schuurmans et al, 1956;Soccol et al, 1994;Steel et al, 1954). Fungi can be grown in submerged cultures by several different morphological forms: suspended mycelia, clumps, or pellets (Metz et al, 1977).…”

Influence of engineering variables upon the morphology of filamentous molds

“…For conditions of isotropic turbulence can be written4" Ul,' = lx E(k,t) dk (7) where ul, is the root mean square of the velocity of all eddies with wave numbers greater than k (m/sec) and E(k,t) is the energy distribution function.…”

The growth of molds in the form of pellets–a literature review

“…They suggested that surface properties of the spores that are influenced by pH are responsible for the coagulation. Steel et al 4 observed filamentous growth for Aspergillus niger a t pH < 5 .…”