Outdoor microalgae cultivation in airlift photobioreactor at high irradiance and temperature conditions: effect of batch and fed-batch strategies, photoinhibition, and temperature stress.

The microalgae Scenedesmus abundans cultivated in five identical airlift photobioreactors (PBRs) in batch and fed-batch modes at the outdoor tropical condition. The microalgae strain S. abundans was found to tolerate high temperature (35-45 °C) and high light intensity (770-1690 µmol m- 2 s- 1). The highest biomass productivities were 152.5-162.5 mg L- 1 day- 1 for fed-batch strategy. The biomass productivity was drastically reduced due to photoinhibition effect at a culture temperature of > 45 °C. The lipid compositions showed fatty acids mainly in the form of saturated and monounsaturated fatty acids (> 80%) in all PBRs with Cetane number more than 51. The fed-batch strategies efficiently produced higher biomass and lipid productivities at harsh outdoor conditions. Furthermore, the microalgae also accumulated omega-3 fatty acid (C18:3) up to 14% (w/w) of total fatty acid at given outdoor condition.

Investigation of polybrominated diphenyl ethers in old consumer products in India.

Polybrominated diphenyl ethers (PBDEs) used extensively over the past 3 decades as flame retardants in most types of polymers, all over the world, have been identified as global pollutants. PBDEs pose various health problems such as thyroid hormone disruption, permanent learning and memory impairment, behavioral changes, hearing deficits, delayed puberty onset, fetal malformations, and possibly cancer. Many measurements of PBDEs in various matrices from Sweden, Holland, Japan, the USA, and elsewhere have been reported, but few measurements are available for India. In this study, a preliminary screening of different congeners of PBDEs has been performed in different old electronic and consumer products with an objective to build capacity in order to analyze PBDEs and BFRs. Six different samples, foam from upholstery, motherboard of a computer, children toy composite sample, old vanishing window blind sample, electrical wire sample, and PVC flooring sample, were collected and analyzed for the presence of the following PBDE congeners: BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, BDE-183, and BDE-209. It was found that three out of six samples were positive for the presence of PBDEs. Three congeners were detected in the samples, i.e., BDE-47, BDE-153, and BDE-209, of which, highest concentration was of BDE-209. Among the samples, motherboard of computer showed the highest concentration of BDE-209 followed by window blind and foam from upholstery. The results of this preliminary investigation indicate that PBDEs are still present in the old consumer products which can be an important additional source of exposure to the population.

Biomethanation of vegetable market waste in an anaerobic baffled reactor: Effect of effluent recirculation and carbon mass balance analysis.

In the present study, feasibility of biomethanation of vegetable market waste in a 4-chambered anaerobic baffled reactor (ABR) was investigated at 30d hydraulic retention time and organic loading rate of 0.5gVS/L/d for one year. Indicators of process stability viz., butyrate/acetate and propionate/acetate ratios were consistent with phase separation in the different chambers, which remained unaltered even during recirculation of effluent. Chemical oxygen demand (COD) and volatile solids (VS) removal efficiencies were observed to be consistently high (above 90%). Corresponding biogas and methane yields of 0.7-0.8L/g VS added/d and 0.42-52L/g VS added/d respectively were among the highest reported in case of AD of vegetable waste in an ABR. Process efficiency of the ABR for vegetable waste methanation, which is indicated by carbon recovery factor showed that, nearly 96.7% of the input carbon considered for mass balance was accounted for in the product.

Dynamics of effluent treatment plant during commissioning of activated sludge process unit.

Industrial effluent treatment plants (ETPs) are very important in protecting the environment and different life forms from harmful industrial waste. Hence, the efficiency of ETPs must be regularly monitored, particularly after major repair or replacement work. Present study evaluated the performance of an ETP over a period of 4 months, during which aeration tank (T1) of the activated sludge unit was replaced with a new one (T2). System had to be maintained operational during this transition, which warranted close monitoring of the system performance due to the daily load of hazardous industrial wastewater. Analysis showed that the raw wastewater was highly variable in composition and contained many hazardous organic and inorganic pollutants, such as heavy metals, bisphenol A and cyanoacetylurea. It showed significant toxicity against HepG2 cells in vitro. However, the ETP was found to successfully treat and detoxify the wastewater. Denaturing gradient gel electrophoresis (DGGE) analysis showed large temporal fluctuations in the ETP microbial community, which is consistent with the variable composition of wastewater. It indicated that functional stability of the ETP was not associated with stability of the microbial community, probably due to high microbial biodiversity and consequently high functional redundancy. In conclusion, the CETP showed consistent level of detoxification and microbial community dynamics after switching to T2, indicating successful development, acclimatization and commissioning of T2.

Stress-induced lipids are unsuitable as a direct biodiesel feedstock: a case study with Chlorella pyrenoidosa.

The effects of various stresses on the suitability of lipid synthesized by Chlorella pyrenoidosa for biodiesel production were investigated. Lipids were characterized for detailed fatty acid methyl ester profiling and biodiesel properties like cetane number (CN), iodine value, cold filter plugging point (CFPP). Maximum biomass productivity (106.63 mgL(-1)d(-1)) and lipid content (29.68%) were obtained at indoor cultivation (nitrate sufficient, pH 8-10, 24h illumination). However, compared to this condition, other nitrate sufficient cultures [pH 6-8 and 10-12 (24h illumination), and at ambient CO2 and 16:8h light:dark photoperiod (pH unadjusted)] showed ∼12-14% lower lipid productivity. Upon 50% nitrate depletion (at indoor and outdoor; pH unadjusted) lipid content has increased by 7.62% and 17%, respectively. Though stress conditions helped enhancing lipid accumulation, there was two-fold increase in PUFA content compared to that observed at pH 8-10. This resulted in fuel properties which did not comply with the biodiesel standards.

Degradative potential of Stenotrophomonas strain HPC383 having genes homologous to dmp operon.

A strain, Stenotrophomonas HPC383 is isolated from effluent treatment plant treating wastewater from pesticide industry; degrades various aromatic compounds (cresols, phenol, catechol, 4methyl-catechol and hydroquinone) and crude oil, as determined through HPLC and GC analysis. Culture HPC383 could degrade (%) various compounds (1 mM) from a mixture: phenol - 99, p-cresol - 100, 4-methylcatechol - 96 and hydroquinone - 43 within 48 h of incubation, whereas it took 7 days to degrade 94% of 0.5% crude oil. Gene locus dmpN, to identify phenol degrading capacity was determined by PCR followed by southern analysis. The sequenced DNA fragment exhibited 99% sequence similarity to phenol hydroxylase gene from Arthrobacter sp. W1 (FJ610336). Amino acid sequence analysis of phenol hydroxylase reveals it to belong to high-Ks (affinity constant) group. Application of HPC383 in bioremediation of aquatic and terrestrial sites contaminated with petrochemical has been suggested.

In situ bioremediation of organochlorine-pesticide-contaminated microcosm soil and evaluation by gene probe.

BACKGROUND: Pesticide-formulating industries are contaminating the environment through various activities. Bioremediation is the best method for decontamination, as chemical and physical methods are not only costly but also not very effective in open field systems. In the present study, in situ bioremediation of organochlorine-contaminated soil was demonstrated by combined biostimulation and bioaugmentation strategies, followed by evaluation using a molecular method. RESULTS: Three parameters were monitored: microbial biomass (colony-forming units (CFU) g(-1) soil), residual pesticides after treatment and catabolic genes from microcosm soil. Both the biostimulation and the bioaugmentation treatments showed an initial lag phase of 80 days towards colony-forming units. Gas chromatography of soil samples showed that concentrations of residual pesticides in the soil declined by up to 85-90% after 80 days, indicating their utilisation with time. On dot-blot hybridisation of the total DNA from the same soil samples, it was observed that catabolic genes tfdC (catechol 1,2-dioxygenase) and cm genes (chlorophenol monoxygenase) were predominant, whereas other catabolic genes such as catechol 2,3-dioxygenase (xylE) were negligible. CONCLUSION: The strategy of in situ bioremediation and its evaluation by gene probe and also by conventional methods was demonstrated for organochlorine-pesticide-contaminated soil in open microcosms. It showed that bioaugmentation along with biostimulation was effective, although initial acclimatization for a period of almost 2-3 months was required in the open field systems.