Production of S. Meliloti Using Wastewater Sludge as a Raw Material: Effect of Nutrient Addition and pH Control

• Published in: Environmental technology Vol. 23; no. 6; pp. 623 - 629
• Main Authors: Ben Rebah, F., Tyagi, R. D., Prevost, D.
• Format: Journal Article
• Language: English
• Published: London Taylor & Francis Group 01.06.2002; Selper
• Subjects: Agriculture; Agronomy. Soil science and plant productions; biofertiliser; Biological and medical sciences; Conservation of Natural Resources; Economic plant physiology; Fabaceae - physiology; Fermentation; Fertilizers; Fundamental and applied biological sciences. Psychology; Hydrogen-Ion Concentration; inoculant; rhizobium; Sewage - chemistry; Sinorhizobium meliloti - physiology; sludge disposal; Sludge recycling; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); Canada; North America; America; Quebec; Waste utilization; Rhizobium meliloti; Glycerol; Environmental factor; Sewage sludge; Sewage treatment plant; Substrate; Yeast extract; Upgrading; Concentration effect; Microorganism culture; pH; Bacteria; Rhizobiaceae; Waste water purification; Inoculum
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593332308618378

The utilization of wastewater sludge as a raw material for the production of legume inoculant is considered as a new viable alternative for recycling. The effect of addition of nutrient sources (yeast extract and glycerol) and the pH control on S. meliloti was investigated in a shake flask and at controlled pH in a 15 l fermentor. Different concentrations of yeast extract (0.5, 1, 2 and 4 g l −1 ) and glycerol (2.5, 5, 7.5 and 10 g l −1 ) were added to the secondary sludge. The cell yield as well as the generation time were affected by the addition of these nutrient sources. The maximum cell yield (8.85×10 9 cfu ml −1 ) was achieved in 32 hours of incubation with the addition of 4 g l −1 of yeast extract. This value was 3.2 times higher than from the non-supplemented sludge. Moreover, at this yeast extract concentration, the cell concentration in the stationary phase did not decrease. The addition of glycerol to sludge samples containing 4 g l −1 of yeast extract further improved the rhizobial growth but not significantly compared with the control. The highest yield (16.5×10 9 cfu ml −1 ) was obtained with 7.5 g l −1 of glycerol and 4 g l −1 of yeast extract. In fermentor experiments, pH did not seem to be a limiting factor and the increase of pH up to 8.85 in uncontrolled fermentor seems to have no effect on rhizobial growth and cell yield.