Production of ethanol from cellulosic biomass by Clostridium thermocellum SS19 in submerged fermentation: screening of nutrients using Plackett-Burman design.

Plackett-Burman design, a statistical methodology, was used to screen 23 nutrients belonging to three categories--carbon, nitrogen, and salt/mineral sources--for the production of ethanol from cellulosic biomass by Clostridium thermocellum SS19 in anaerobic submerged fermentation. In this design, just n number of experiments is required for screening n-1 variables. The experimental data were subjected to statistical analysis for calculating the regression coefficients and t-values. Filter paper, Solka Floc, corn steep liquor (CSL), cysteine HCl, magnesium chloride, and ferrous sulfate showed relatively higher regression coefficients on ethanol production and growth. Among the 23 nutrients screened, based on their performance in terms of product-promoting ability, availability, and cost, filter paper, CSL, cysteine HCl, magnesium chloride, and ferrous sulfate were identified as the most effective and, therefore, selected for inclusion in further optimization studies.

Fermentation of cellulose to acetic acid by Clostridium lentocellum SG6: induction of sporulation and effect of buffering agent on acetic acid production.

AIMS: To determine the growth, correlation between sporulation and acetic acid production and effect of buffering agent at high substrate cellulose concentrations of the strain Clostiridium lentocellum SG6. METHODS AND RESULTS: The strain SG6 was grown in cellulose mineral salt medium containing cellulose (Whatman No. 1 filter paper, Whatmore International Ltd., Maidstone, UK) or cellobiose. The strain fermented cellulose even after several transfers on cellobiose medium. The formation of endospores on third day onwards indicated the lowering of pH in the medium because of the formation of acetic acid. Maintaining the pH 7.2 at higher substrate concentrations resulted in increase of biomass, cellulose fermentation, acetic acid production, etc. CONCLUSIONS: The strain SG6, with its high fermentation yields and sporulating character can become a potential strain for acetic acid production and also as a probiotic strain in animal nutrition. SIGNIFICANCE AND IMPACT OF THE STUDY: The direct conversion of cellulosic biomass to acetic acid can eliminate expensive three-step saccharification, fermentation processes. The strain SG6 can ferment cellulose at high substrate concentrations.

Clostridium lentocellum SG6--a potential organism for fermentation of cellulose to acetic acid.

A cellulolytic, acetic acid producing anaerobic bacterial isolate, Gram negative, rod-shaped, motile, terminal oval shaped endospore forming bacterium identified as Clostridium lentocellum SG6 based on physiological and biochemical characteristics. It produced acetic acid as a major end product from cellulose fermentation at 37 degrees C and pH 7.2. Acetic acid production was 0.67 g/g cellulose substrate utilized in cellulose mineral salt (CMS) medium. Yeast extract (0.4%) was the best nitrogen source among the various nitrogenous nutrients tested in production medium containing 0.8% cellulose as substrate. No additional vitamins or trace elemental solution were required for acetic acid fermentation. This is the highest acetic acid fermentation yield in monoculture fermentation for direct conversion of cellulose to acetic acid.

Effect of various flours on the production of thermostable beta-amylase and pullulanase by Clostridium thermosulfurogenes SV2.

The effects of various flours on production of thermostable beta-amylase and pullulanase using Clostridium thermosulfurogenes SV2 was studied in submerged fermentation. Among the flours added to PYE basal medium, potato flour was the best substrate for enzyme production, and under optimal conditions C. thermosulfurogenes SV2 produced 0.87 and 0.98 U of thermostable beta-amylase and pullulanase, respectively, per ml culture broth.

Improved ethanol tolerance and production in strains of Clostridium thermocellum.

Two Clostridium thermocellum strains were improved for ethanol tolerance, to 5% (v/v), by gradual adaptation and mutation. The best mutant gave an ethanol yield of 0.37 g/g substrate, with a growth yield 1.5 times more than its parent. Accumulation of acids and reducing sugars by the mutant strain with 5% (v/v) ethanol was lower than that of the parent strain with 1.5% (v/v) ethanol.

Improvement of methanogenesis from cow dung and poultry litter waste digesters by addition of iron.

When 50MM FeSO4 was added to cow dung and poultry litter waste which had been processed in daily-fed batch digesters, digesters subsequently unfed showed a faster conversion of substrate and overloaded digesters stabilized within 48 h. Early stabilization of digesters was achieved by adding 20 or 50MM FeSO4 though the latter concentration was faster. When 20MM FeSO4 was added to the daily-fed cow dung and poultry litter waste digesters, it increased methanogenesis by 40% and 42%, respectively, and increased the turnover rate of total solids, volatile solids and volatile fatty acids and the number of methanogens.

Characteristics of Clostridium thermocellum strain SS8: A broad saccharolytic thermophile.

Clostridium thermocellum SS8 produced both carboxymethylcellulase (CMCase) and Avicelase when grown on cellulose. CMCase activity was unaffected by Ca(2+), Mg(2+), dithionate or dithiothreitol (DTT). Avicelase activity increased 2-fold with 5 mM DTT and 10 mM Ca(2+). Cellulase and amylase were produced when a celluloseadapted culture was grown on starch. The mould grew best on sucrose and was inhibited by NaCl above 10 g/l.

Production of ethanol from straw and bamboo pulp by primary isolates of Clostridium thermocellum.

Clostridium thermocellum strains SS8 and GS1 grew poorly on crude blopolymers but termented them easily after alkall treatment. With 1% alkall-extracted rice straw (AERS) and dellgnified bamboo pulp (DBP), the ethanol-to-substrate (E/S) ratios were almost the same as those obtained when using fillter paper. Increasing the substrate concentrations decreased the percentage substrate degraded and the E/S ratio and concomitantly increased the amount of reducing sugars accumulated. A maximum amount of 8.6 g ethanol/l was produced by strain SS8 out of 37.5 g DBP degraded. Strain GS1 accumulated reducing sugars at substrate concentrations >50 g/l, thereby accounting for about 70% of AERS degraded. This strain produced cellulase on both cellulose and cellobiose. Both the strains grew in the presence of 1.5% (v/v) ethanol. Strain SS8 fermented starch, but the ethanol yield was low compared to that from cellulose. About 75% of starch degraded accumulated as reducing sugars at a substrate concentration of 40 g/l. The Inhibitory effects of ethanol (2 to 4%) were less drastic when growing cultures were challenged than when they were formed in situ. The effect of ethanol depended upon the phase of the culture.

Physico-chemical interactions and bioconcentration of zinc and lead in the industrially polluted Husainsagar Lake, Hyderabad, India.

This paper deals with the interactions of different physico-chemical parameters in the water profile, and the bioconcentration of zinc and lead in Husainsagar Lake, India. The concentrations of both the metals are within the permissible limits (Indian Council of Medical Research, New Delhi, India (1975). Manual of Standards of Quality for Drinking Water Supplies. ICMR Special Report, p. 44). The concentration of Zn and Pb in the vertical profile were highest in the bottom stratum of the lake and least in the surface stratum. Their concentrations were two to three thousand-fold more in surficial sediments than in the overlying water column. The concentration of Zn increased with increasing trophic level from nanoplankton to zooplankton, but not to fish, and the concentration of Pb decreased with increasing trophic level: nanoplankton --> phytoplankton --> zooplankton --> fish, illustrating no bioconcentration of metals in the classic sense of the term as has been noted for mercury and chlorinated hydrocarbons (DDT).