Effects Of Low-temperature Pretreatments Research Articles

The effect of low-temperature pretreatment on the solubilization and biomethane potential of microalgae biomass grown in synthetic and wastewater media

Microalgae have been suggested as a sustainable raw material for biofuel production in the form of methane via anaerobic digestion. Here, pretreatments at 60–80°C were investigated, aiming to study the impact of algae culture media on biomethane potential and pretreatment efficiency. Chlorella vulgaris and mixed culture of native algae species (dominating by Scenedesmus sp.) were grown in synthetic medium, wastewater (sterilized and non-sterilized) and digestate from anaerobic digestion of pulp and paper biosludge (sterilized and non-sterilized). The biomethane potential for native microalgal biomass varied between 154 and 252LCH4kg−1 VS depending on culture media. The efficiency of the low-temperature pretreatment (80°C, 3h) for solubilization (9–12%) of C. vulgaris and native algae biomass was similar for algae grown in sterilized and non-sterilized wastewater media. The pretreatment increased the biomethane potential of native algae biomass by 11–24%.

Impact of low temperature pretreatment on the anaerobic digestion of microalgal biomass

The aim of this study was to investigate the effect of low temperature pretreatment on the anaerobic digestion of microalgal biomass grown in wastewater. To this end, microalgae were pretreated at low temperatures (55, 75 and 95°C) for 5, 10 and 15 h. Biomass solubilisation was enhanced with the pretreatment temperature and exposure time up to 10h. The methane yield was improved by 14%, 53% and 62% at 55, 75 and 95°C, respectively; and was correlated with the solubilisation increase. The pretreatment at 95°C for 10h increased VS solubilisation by 1188%, the initial methane production rate by 90% and final methane yield by 60% compared to untreated microalgae. With diluted biomass (∼1% VS) positive energy balance was not likely to be attained. However, with concentrated biomass (>2% VS) energy requirements may be covered and even surplus energy generated.

Effect of Low Temperature Pre-Treatment on Anther Culture in Selected Indica, Japonica Rice Varieties and their Inter Sub-Specific Hybrids

Effect of cold pre-treatment of panicles with reduced temperatures (of 5°C, 7°C, 8°C and 10°C) and exposure for different time durations (at weekly intervals up to 4 weeks) on anther culture of Japonica rice variety Hu lo tao, Indica rice varieties Bg 90-2, Bg 379-2 and their F1 hybrids for high frequency callus induction and plant regeneration was investigated. Anthers were cultured in N6 medium with 5% sucrose, 2 mg l-1 2,4 D and 0.5 mg l-1 Kinetin. The cultures were kept in the dark at 28 ± 2°C for callus induction. Induced calli of 1-2 mm diameter were transferred to half strength Murashige and Skoog (MS) medium supplemented with 2.0 mg l-1 Kinetin and 0.5 mg l-1 NAA. The effect of variety and cold pre-treatment was significant at 5% probability level. The Indica varieties had the lowest callus induction frequency (0.3% - 7.0%). Japonica and Japonica × Indica hybrids had high callus induction (12.3% - 70.0%). The F1 hybrid Hu lo tao × Bg 90-2 had comparatively high callus induction (31.0% - 70.0%) than the other genotypes. Japonica variety Hu lo tao and F1 hybrids had highest callus development at cold pre-treatment at 8°C for 14 and 21 days. The highest green plant regeneration was observed in F1 hybrid, Hu lo tao × Bg 90-2 followed by Japonica variety subjected to 8°C for 14 days. Very poor green plant regeneration was observed in Indica variety, Bg 90-2 when it was exposed to 7°C for 21 and 28 days. Variety Bg 379-2 did not produce any green plant at any treatment. The F1 hybrid Hu lo tao × Bg 379-2 produced lower green plants than F1 hybrid Hu lo tao × Bg 90-2. Cold pre treatment at 8°C temperature for 14 days was found to be most effective for anther culture in experimental genotypes used in the study. Key words: variety, cold pre-treatment, callus induction, plant regeneration, rice DOI: 10.4038/cjsbs.v38i1.1322 Cey. J. Sci. (Bio. Sci.) 38 (1): 11-16, 2009

Effect of Low Temperature Pretreatment of Buds or Inflorescence on Isolated Microspore Culture in Brassica rapa(syn. B.campestris).

The effect of low temperature pretreatment of buds or inflorescence on microspore culture for the production of haploids of Brassica rapa (syn. B.campestris) was examined. Incubation of the buds or the inflorescence at 4°C for 3 or 10 days before the culture of microspores induced efficient microspore embryogenesis. Pretreatment of flower buds was more effective than that of the inflorescence. Prolonged pretreatment up to 20 days promoted embryo induction. Microspores in the buds were examined for developmental stage before and after the pretreatment. Buds with a petal length to anther length ratio of about 0.5-0.7, which had microspores were at the late unicellular stage, were collected and were used. All microspores were at the late unicellular stage before the pretreatment. The percentage of the microspores at the stage of late unicellular decreased during the pretreatment while the percentage of bicellular stage microspores with two unequal size nuclei increased. At the same time, a small but notable number of bicellular stage microspores with equal size nuclei, which is the first step of microspore embryogenesis, was observed after the pretreatment.

Effect of low temperature pre-treatment on infection of clover root hairs by Rhizobium

Holding 24-h seedlings ofTrifolium spp. at 3°C increased the number of root hairs infected byRhizobium when the plants were subsequently inoculated and grown at 19°C. This effect was transitory, disappearing on plants more than 7 days old.