Lactic acid has been first introduced to us as early as 1780 as a sour component of milk. Ever since we have found its applications in food, pharmaceutical, cosmetic industries etc. Now there are emerging uses as a potential feedstock for the biodegradable polymer industry. The microorganisms being used for lactic acid fermentation, the raw materials reported, the various novel fermentation processes and its processing methods have been reviewed. The properties and applications of lactic acid, its derivatives and polymer have been discussed. The various routes to polymerization and the companies presently involved in lactic acid production have been covered.
AbstractThe possibility of applying an integrated technique of oil agglomeration and biofilm formation for recovery of coal fines from coal washeries and power plants effluents has been explored. Laboratory experiments with simulated slurries of different Indian coal fines demonstrate that vegetable oils are satisfactory agglomerating agents for recovery of most of the coal fines depending on the nature of coal and type of oil. The agglomeration behaviour of coal fines was assessed in terms of % yield, % organic matter recovery and % ash rejections. Maximum 85% agglomerate recovery was obtained in the agglomeration stage. Residual oil concentrations in some cases were found to exceed the permissible limit. Recovery of residual coal fines and reduction in residual oil concentration in the resultant slurry after oil agglomeration have been attempted using biofilm formation. A laboratory scale treatment reactor was put under complete recirculation to facilitate attached microbial growth on coal particles as carrier under aerobic conditions. The influence of various parameters on attached growth and stable biofilm formation were studied. The growth patterns of attached cell in suspension and consumption pattern of carbon substrate (oil) have been investigated. Steady decline in residual substrate concentration in the slurry with corresponding increase in the growth of attached and free cell mass is observed. The growth process was favoured in pH range of 6.5-7.0. The attached growth was found to be expanded in size in due course of time ultimately leading to the formation of stable biofilm in the treatment reactor which was subjected to the influent total suspended solids loading resulting from oil agglomeration step. Performance of the biofilm reactor in terms of % reduction in total suspended solids and residual oil concentration in the influent slurry was assessed in continuous mode. Complete recovery of coal fines and 60% degradation of oil was observed in the final effluent discharged from the treatment reactor.Key Words: Recovery of coal finesoil agglomerationbiofilm formation Additional informationNotes on contributorsSurekha SharmaJoyce Laing works in the Department of Child and Family Psychiatry, Playfield House, Cupar, Fife, and is a Consultant Art Therapist to Psychiatric Hospitals and Prisons and Chairwoman of the Scottish Society of Art and Psychology.
A simple variation of Monod kinetics is presented which describes extended lag phases observed in microbial cultivation. This variation of Monod kinetics can be expressed in a compact exponential form and is used to explain the adaptation of mixed cultures to adverse environmental conditions. The performance of the Monod model and the proposed exponential model in predicting the behavior of a mixed culture exposed to high nitrate concentrations are compared. A parameter for nitrate degradation is defined which is correlated to changes in the maximum specific growth rate as the culture adapts to increasing concentrations of nitrate.
Batch biosorption of chromium(VI) from an aqueous solution was studied using dry biomass of Fusarium sp. isolated from soil. At the initial metal ion concentration of 50mg∕L and pH 2.0, the Cr(VI) adsorbed was 12.5mg∕g of adsorbent. The Cr(VI) adsorbed increased with increasing initial metal ion concentration up to 500mg∕L. A maximum removal of 47.5mg∕g was observed at pH 2.0 at 500mg∕L initial Cr(VI) concentration. An increase in pH from 2 to 6 decreased Cr(VI) removal from 12.5to2.2mg∕g at 50mg∕L metal ion concentration. At all the concentrations, the adsorption equilibrium was obtained within 2h. The adsorption equilibrium constants were obtained from both Freundlich and Langmuir adsorption isotherms. The organism was also found to remove 42.5mg of Cr(VI) per gram of adsorbent from an effluent (500mg∕L) generated from an electroplating industry.
In the present work biological removal of Cr(VI) was carried out in fed batch mode of operation using the growing cells of Fusarium solani isolated from soil. The fed batch process was studied by constant volume pulse feeding (CVPF) and increasing volume pulse feeding (IVPF), and the effects of these operational strategies on biological performance were compared with a conventional batch process. Batch studies indicated the maximum specific Cr(VI) removal to be 71 mg/g at pH 5.0 and at 500 mg/l initial Cr(VI) ion concentration. In CVPF process the maximum specific Cr(VI) removal was found to be 35.51 mg/g and 25.15 mg/g as compared to 51.9 mg/g and 42.5 mg/g obtained in IVPF during first and second pulse feedings respectively in both the cases. These results were compared with the Cr(VI) removal obtained in earlier studies conducted by the present authors using the continuous mode of operation. The continuous mode of operation was found to be the best operational strategy in which the process could be operated for longer duration with maximum specific Cr(VI) removal of 62.27 mg/g. Nearly complete removal was obtained using single stage reactor at lower Cr(VI) concentrations up to 100 mg/l and a multi stage reactor at higher Cr(VI) concentration.
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