A novel fed-batch digestion system for biomethanation of plant biomasses.

Plant biomasses, which in the absence of adequate pretreatment pose serious operational problems in biogas production using conventional domestic flow-through digesters, can be successfully digested in a novel fedbatch digestion system that produces a steady rate of biogas. Basically, the system is a batch digestion operated with a regular input of a calculated amount of feed based on first order decay kinetics in order to maintain a regular biogas production rate. For nearly three years the system was tested in a laboratory-scale fed-batch digester (10 l) using dried water hyacinth as feed providing the desired biogas production rate. A field-scale domestic digester of masonry construction with a working volume of 10 m3 was designed and tested for about 9 months by feeding a mixture of dried water hyacinth or banana stem along with sugarcane press mud, yielding an average biogas production of 90-100% of the expected rate calculated on the basis of the feed rate.

A comparison of peak expiratory flow rates obtained with the Morgan Spirocheck and a Mini Peak Flow Meter.

To examine whether the normal Indian standards of Peak Expiratory Flow Rate (PEF) established with the peak flow meter were applicable to PEF values obtained with the Morgan Spirocheck, a comparison was made of PEF(S) measured with the Spirocheck with PEF (M) obtained with a Mini Peak Flow Meter. Data were obtained in 92 subjects (53 males between 20 and 84 years of age and 39 females between 21 and 75 years), comprising staff of the institute, patients undergoing treatment for chronic arthritis, and the accompanying relatives. There was a highly significant correlation between the two values. The values were identical in 14 subjects; the differences between the values were within 10% in 54 subjects, and in excess of 10% in only 20 subjects. In the whole group, the mean and standard error were 363.5 +/- 14.7 and 384 +/- 15.2 lit/min for PEF (S) and PEF (M) respectively. The regression equation PEF (M) = 0.961 x PEF (S) + 34.9 will enable estimation of expected value of PEF (M) corresponding to the observed value of PEF (S) when a standard obtained with a Peak Flow Meter in used assess abnormality in a patient.

Metabolic blocks in the degradation of beta-sitosterol by a plasmid-cured strain of Arthrobacter oxydans.

Plasmid-harbouring, sterol-decomposing organism Arthrobacter oxydans 317 was treated with sodium dodecylsulphate to obtain a plasmid-cured strain A. oxydans 317 A1 incapable of utilizing 4-androstene-3,17-dione (AD). The strain 317 A1 was unable to degrade beta-sitosterol side chain completely to form AD but could carry out partial degradation as shown by the accumulation of 3-oxochol-4-en-24-oic acid as a major metabolite and 27-norcholest-4-en-3,24-dione as a minor metabolite. The strain could form 1,4-androstadiene-3,17-dione (ADD) from 3-oxo-23,24-bisnorchol-1,4-dien-22- oic acid (BNC) to a limited extent. The existence of metabolic blocks in the conversion of 3-oxochol-4-en-24-oic acid to 3-oxo-23,24-bis-norchol-4-en-22-oic acid and further conversion to AD by the plasmid-cured strain 317 A1 was suggested. Neither the formation of ADD from AD nor the conversion of AD and ADD to 9 alpha-hydroxy derivatives leading to steroid ring opening could be done by the plasmid-cured strain but the 17 beta-reduction of AD and ADD and 1(2)-reduction of ADD were not affected by the absence of the plasmid. It was proposed that plasmid determines 1(2)-dehydrogenation and 9 alpha-hydroxylation of steroid ring structure in this organism.

Different modes of hydrocarbon uptake by two Pseudomonas species.

The mode of n-hexadecane uptake by two organisms-Pseudomonas M 1 and Pseudomonas N 1-was studied. During the growth of Pseudomonas M 1 on n-hexadecane, no extracellular biosurfactant/bioemulsifier was produced, no significant n-hexadecane pseudosolubilization was observed, and the reduction of surface and interfacial tensions in the cell-free culture broth was negligible. EDTA, a known inhibitor of hydrocarbon pseudosolubilization, did not inhibit the growth of the organism on n-hexadecane. Normal hexadecane-grown cells showed strong surface-active properties and capacity to adhere firmly to hydrocarbon phase. It was concluded that in this organism, surface-active properties of the cells facilitate attachment of cells to the hydrocarbon-water interface generated by agitation, and promote substrate uptake and growth; no hydrocarbon pseudosolubilization or extracellular mediator is involved in the substrate uptake. Pseudomonas N 1 grew on n-hexadecane much faster than Pseudomonas M 1. Growth of this organism on n-hexadecane was associated with the extracellular production of biosurfactant-bioemulsifier and n-hexadecane pseudosolubilizing factor; the growth was strongly inhibited by 5 mM EDTA, indicating that hydrocarbon pseudosolubilization was the dominant factor in substrate uptake. The rate of n-hexadecane pseudosolubilization was high enough to account for the substrate up take rate. Hydrocarbon emulsifying and n-hexadecane pseudosolubilizing factors were isolated and tentatively characterized as lipoprotein and glycoprotein, respectively. Both factors act in a synergistic manner to provide enhanced hydrocarbon transport to cells through pseudosolubilization. It is proposed that this facility of mediated hydrocarbon transport is the basis for the relatively fast rate of growth of Pseudomonas N 1 on hydrocarbon.

Factors limiting the microbial conversion of sterols to 17-ketosteroids in the presence of metal chelate inhibitors.

Bioconversion of sterols to 17-ketosteroids by an Arthrobacter species occurred in the presence of hydrophobic metal-chelating agents but the production of 17-ketosteroids (17-KS) was seriously limited by the rapid loss of the viability of cells in the presence of these inhibitors. Besides, the conversion was inhibited by 17-KS at concentrations of 500 ppm or more. The 17-KS formed consisted exclusively of 1,4-androstadiene-3,17-dione (ADD) and 4-androstene-3,17-dione (AD) and these were found in the extracellular medium predominantly in bound form or as molecular aggregates which may limit their accumulation. It was concluded that enhanced production of 17-KS could be achieved by protecting the viability of cells and by removing the steroid metabolites from the site of inhibition.

Mode of uptake of insoluble solid substrates by microorganisms. I: Sterol uptake by an arthrobacter species.

The mode of uptake of sterols, which are nearly insoluble in water by an Arthrobacter species, was studied on the basis of substrate transfer via the aqueous phase (solubilization/pseudosolubilization) and through direct contact with sterol particles. Growth of the organism, on stero powder was predominantly in nonlogarithmic in character, indicating a possible limitation of substrate transfer. Soluble sterol was shown to be the preferential form of the substrate for assimilation by the organism. Evidence was obtained for increased solubilizition of beta-sitosterol and cholesterol during microbial growth on these substrates. But the rate of solubilization of beta-sitosterol (3.06 mg L(-1) h(-1)) was too inadequate to account for the observed substrate uptake rare (107 mg L(-1) h(-1)) during growth. A cholesterol solubilization rate of 44 mg L(-1) h(-1) could, however, account to an appreciable extent for the observed cholesterol uptake rate of 140 mg L(-1) h(-1) during growth. Increasing attachement of cells to sterol particles during growth was observed by microscopic examination, indicating that growth may take place over the surface of sterol particles. By using the synthetic surfactant HYOXYD AAO (alkyl aryl polyglycol ether), which prevented attachment of cells to sterol particles without affecting the metabolic integrity of the cells, it was shown that growth indeed took place predominantly on the surface of the sterol particles. Increased generation of finer particles of sterol, which provides increased substrate surface area during growth, was demonstrated. It was concluded that with beta-sitosterol, growth takes place almost entirely by attachement, whereas with cholesterol, about 30% of the growth take place on solubilized substrate and the rest through attachament.

Mode of uptake of insoluble solid substrates by microorganisms. II: Uptake of solid n-alkanes by yeast and bacterial species.

Using two species of yeast and one of bacterium, evidence has ben obtained which indicates that the microbial uptake of solid alkane powders occurs primarily through a substrate solubilization mechanism. EDTA, a strong inhibitor of hydrocarbon solubilization by the cells, inhibited the growth of these organisms on alkane powder; the inhibition could be removed vai a supply of artificially solubilized alkane. One of the yeast strians, which was a mutant incapable of growing on solid alkane powder and liquid alkane, could grow very well on artifically solubilized alkanes. It was demonstrated that the solid alkane solubilization rate during microbial growth could satisfactorily account for the maximal alkane uptake rate actully observed during growth. The specificity of solubilization for the solid alkane used as the growth substrate was demonstrated.

Isolation and functional characterization of hydrocarbon emulsifying and solubilizing factors produced by a Pseudomonas species.

Pseudomonas PG-1 cultivated on pristane produced in good amount a heat-stable polymeric substance which showed strong hydrocarbon emulsifying and solubilizing properties. The substance was isolated in crude form and was found to contain 34% protein, 16% carbohydrate, and 40% lipid. The hydrocarbon solubilizing activity of the isolate was strongly inhibited by EDTA but the chelating agent had no effect on the hydrocarbon emulsifying activity. Both activities of the isolate were strongly inhibited by chymotrypsin treatment indicating the importance of the protein moiety for its activity. Hydrocarbon solubilization by the isolate showed a certain degree of specificity to pristane in modest agitation generally used in microbial cultivation, but this specificity was lost by vigorous agitation in a Waring blender. It was proposed that in the first case, solubilization was effected by a solubilizing factor specific to pristane, whereas in the latter case, nonspecific solubilization occurred due to the action of the emulsifying factor. The rate of pristane solubilization by heat-treated culture broth under the conditions of agitation used in cultivation (rotary shaker, 120 rpm) was found to be ca. 750 mg L(-1) h(-1) which was much larger than the maximal pristane uptake rate of 170 mg L(-1) h(-1) observed during microbial growth on the substrate. It was concluded that hydrocarbon solubilization could satisfactorily account for the substrate uptake and growth.

Predominant role of hydrocarbon solubilization in the microbial uptake of hydrocarbons.

Using EDTA and proteolytic enzymes to suppress hydrocarbon solubilization, direct evidence is presented in support of the mechanism of liquid hydrocarbon uptake by microbial cells predominantly from the solubilized or accommodated substrate. EDTA (2-5mM) strongly inhibited growth of three yeast species and one bacterial species on n-hexadecane and the inhibition was removed by surfactant-emulsified and surfactant-solubilized alkane and also by excess addition of Ca(2+). EDTA had no inhibitory effect on the growth of the organisms on soluble substrates such as sodium acetate and nutrient broth or on n-pentane, a volatile alkane which was primarily transported by diffusion from gas phase. EDTA was shown to have no significant effect on the adsorption of cells on alkane drops. EDTA inhibition of growth was considered to be due to suppression of alkane solubilization, brought about by the solubilizing factor(s) produced by cells. It was shown that this chelating agent did not inhibit the growth of yeast on solubilized alkane but strongly inhibited its growth on alkane drops. It was demonstrated that adherent capacity of microbial cell to oil phase was closely related to the state of hydrocarbon emulsification and had no relationship to the ability of organisms to grow on hydrocarbon. Certain proteolytic enzymes inhibited the growth of yeast on alkane, presumably by digesting the alkane solubilizing protein, but not on glucose, and the inhibition was removed by a supply of surfactant-emulsified and surfactant-solubilized alkane. Specific solubilization of various hydrocarbon types during growth of the prokaryotic bacterial strain was demonstrated. The specific solubilization of hydrocarbon was strongly inhibited strain was demonstrated. The specific solubilization of hydrocarbon was strongly inhibited by EDTA, and the inhibition was removed by excess Ca(2+). It was concluded that specific solubilization of hydrocarbons is an important mechanism in the microbial uptake of hydrocarbons.

Peak expiratory flow rate in South Indian adults.

Peak Expiratory Flow Rate (PEFR) was measured with a Wright Peak Flow Meter in 851 healthy men and women of two categories; Group I--students and staff of the Medical College constituting the middle income group, and Group II--healthy individuals from the poorer class with an income of less than Rs.200/-per month, forming the lower income group. In both categories women had much lower values than men, and in both sexes the values in the subjects of the poor income group was significantly lower. The PEFR was found to correlate best with height in subjects below 30 years, and with age in older subjects. The mean values, standard deviations and regression equations are given for the different groups. Present values are also compared with some western and Indian data.

A study of menarcheal age in India.

A study of menarcheal age was carried out in southern India. A logit method of analysis was applied to status quo data on 1267 Tamil and Telugu speaking girls aged 9 to 18 years in 3 schools catering for different socio-economic groups. There appears to be no relationship of menarcheal age with dietary pattern classified simply as vegetarian and non-vegetarian. Differences in median age at menarche between schools correspond well with the socio-economic differences between them. The median age in the most advantaged school (12-86 years) is comparable with that in recent studies in southern and eastern Europe, and may perhaps be in advance of some recent north-west European samples.