Coffee husk: an inexpensive substrate for production of citric acid by Aspergillus niger in a solid-state fermentation system.

Aspergillus niger CFTRI 30 produced 1.3 g citric acid/10 g dry coffee husk in 72 h solid-state fermentation when the substrate was moistened with 0.075 M NaOH solution. Production was increased by 17% by adding a mixture of iron, copper and zinc to the medium but enrichment of the moist solid medium with (NH4)2SO4, sucrose or any of four enzymes did not improve production. The production of about 1.5 g citric acid/10 g dry coffee husk at a conversion of 82% (based on sugar consumed) under standardized conditions demonstrates the commercial potential of using the husk in this way.

Sugarcane-pressmud as a novel substrate for production of citric acid by solid-state fermentation.

Sugarcane-pressmud, a by-product of cane-sugar manufacture, was used as a substrate for production of citric acid by Aspergillus niger CFTRI 30, in a solid-state fermentation system. Of the 170 g of sugar supplied, 131 g were consumed, with a 79% yield of citric acid over 120 h. Potassium ferrocyanide improved the conversion to about 88% and lowered the fermentation time by 24 h. Enrichment with sugar and NH4NO3 was essential to improve productivity. About 174 g citric acid/kg dry sugarcane-pressmud were produced after 120 h in ferrocyanid-treated medium which initially contained 12.5% (w/w) effective sugar and 0.1% (w/w) NH4NO3. About 3% (w/w) of the original sugar present in the sugarcane-pressmud was non-utilizable. This is the first report on the potential of sugarcane-pressmud for citric acid production.

Potential of solid state fermentation for production of ergot alkaloids.

Production of total ergot alkaloids by Claviceps fusiformis in solid state fermentation was 3.9 times higher compared to that in submerged fermentation. Production was equal in the case of Claviceps purpurea but the spectra of alkaloids were advantageous with the use of solid state fermentation. The data establish potential of solid state fermentation which was not explored earlier for production of ergot alkaloids.

Importance of medium pH in solid state fermentation for growth of Schwanniomyces castellii.

Utilization of soluble starch by Schwanniomyces castellii in a solid state fermentation system was highest in unbuffered medium when initial and final pH of the medium were 6.5-7.0 and 4.0-4.6, respectively. An economic strategy involving the use of urea as a sole nitrogen source in medium with initial pH of 6.5 allowed maximum substrate utilization in the absence of buffer and without any contamination in column fermenter.

Cultural stability of Streptomyces fradiae in the production of xylose isomerase: studies in shake flasks.

Comprehensive studies of pure colonies of Streptomyces fradiae in the production of xylose isomerase by submerged fermentation at shake flask level revealed poor culture stability with respect to enzyme production, biomass formation, degree of pigmentation, quantity of glucose and xylose utilization, level of enzyme in cell-free culture broth and final pH of the fermentation medium. The results serve to stress obligatory evaluation of culture stability of Streptomyces strains in determining their suitability for use in developing fermentation processes for commercial exploitation.

Gibberellic acid by solid state fermentation: Consistent and improved yields.

Five strains each of Gibberella fujikuroi and Fusarium monoliforme were screened to select G. fujikuroi P-3, a strain capable of giving consistent production of gibberellic acid (GA(3)) by solid state fermentation (SSF). The comparative production of GA(3) by SSF and submerged fermentation (SmF) indicated better productivity with the former technique. The accumulation of GA(3) was 1.626 times higher in the case of SSF. On the basis of available carbohydrates in the media, the percent conversions were 0.096 and 0.156 in SmF and SSF, respectively. The use of coarse wheat bran of the particle size of 0.3-0.4 cm resulted in an increase of 2.5 times in the yield of GA(3). The enrichment of commercial wheat bran with soluble starch gave enhanced accumulation to an extent of 3.5 times. The relation between GA(3) production and cell growth in SSF was similar to that encountered in SmF. The consistent and improved yields to a tune of 1.22 g GA(3) per kilogram dry moldy bran (DMB) establish the potential and feasibility of SSF for the production of GA(3) by G. fujikuroi P-3. On preliminary cost analysis, a net savings of about 60% and 50% on fermentation medium cost and the expenditure on down-stream processing, respectively, as compared to the presently employed SmF technique was evident.

Simple method for inducing ascospore formation in yeasts.

A new method for inducing ascospore formation in yeasts is described and compared with conventional methods for its performance. The method has the advantage of simplicity, reproducibility, and saving of time.