Citric acid production from whey with sugars and additives by Aspergillus niger

Citric acid (CA) production by Aspergillus niger ATCC9642 from whey with different concentrations of sucrose, glucose, fructose, galactose riboflavin, tricalcium phosphate and methanol in surface culture process was studied. It was found that whey with 15% (w/v) sucrose with or without 1% methanol was the most favourable medium producing the highest amount (106.5 g/l) of citric acid. Lower CA was produced from whey with other concentrations of sugars and other additives used. Highest biomass of A. niger was produced with the addition of riboflavins. In general, extension of the fermentation (up to 20 days) resulted in an increase in CA and biomass, and decrease in both residual sucrose and pH values. Key words: Citric acid, Aspergillus niger, whey fermentation, surface culture. African Journal of Biotechnology Vol.2(10) 2003: 356-35

Hydrothermal deposition of CdS on vertically aligned ZnO nanorods for photoelectrochemical solar cell application

CdS/ZnO nanorods composite nanofilms were successfully synthesized via hydrothermal method on indium doped tin oxide glass substrates. Sequentially deposited CdS formed cauliflower like nanostructures on vertically aligned ZnO nanorods. The morphological, compositional, structural and optical properties of the films were characterized by field emission scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction and ultraviolet–visible spectroscopy. Photoelectrochemical conversion efficiencies were evaluated by photocurrent measurements in a mixture of Na2S and Na2SO3 akaline aqueous solution. The amount of deposit, as well as the diameter and crystallinity of the CdS cauliflower were found to increase with growth time. CdS/ZnO nanorods composite exhibited greater photocurrent response than ZnO nanorod arrays. Besides, the composite film with 90 min of growth duration displayed the highest photocurrent density which is nearly four times greater than plain ZnO nanorods under the illumination of halogen light. The result exhibited remarkable photoconversion efficiency (η) of 1.92 %

Citric acid production from whey with sugars and additives by Aspergillus niger

Citric acid (CA) production by Aspergillus niger ATCC9642 from whey with different concentrations of sucrose, glucose, fructose, galactose riboflavin, tricalcium phosphate and methanol in surface culture process was studied. It was found that whey with 15% (w/v) sucrose with or without 1% methanol was the most favourable medium producing the highest amount (106.5 g/l) of citric acid. Lower CA was produced from whey with other concentrations of sugars and other additives used. Highest biomass of A. niger was produced with the addition of riboflavins. In general, extension of the fermentation (up to 20 days) resulted in an increase in CA and biomass, and decrease in both residual sucrose and pH values

Microbial bioconversion of palm oil mill effluent to citric acid with optimum process conditions

Oil palm industry has an important role in contributing to the Malaysian economy. Several million tonnes of crude palm oil is produced annually and approximately, about 10 million tonnes of palm oil mill effluent (POME) (highly polluted organic effluent) is generated every year. Citric acid is a commercially valuable product widely used in many industries. More than 400,000 tonnes of citric acid is produced annually by fermentation of expensive raw materials like glucose and sucrose. Efficient and effective methods of producing citric acid from different cheaper raw materials have been of great interest to many researchers, due to its extensive use. This study is an effort to achieve the goal by introducing a new substrate POME and a potential isolated strain of Asperillus niger. The method used was liquid state bioconversion with optimum process conditions obtained from our previous studies using central composite design (CCD)from Minitab software. The optimized parameters were temperature, agitation rate, inoculum size and pH. Analysis has been done everyday up to seven days of fermentation. Performance of the developed process was evaluated on the basis of maximum citric acid (5.24 g/L), chemical oxygen demand removal (COD), total suspended solid (TSS) and removal of heavy metals (cadmium chromium and copper)