ABSTRACT
Microalgal cultures are a clean and sustainable means to use solar energy for CO2 fixation and fuel production. Microalgae grow efficiently and are rich in oil, but recovering that oil is typically expensive and consumes much energy. Therefore, effective and low-cost techniques for microalgal disruption and oil or lipid extraction are required by the algal biofuel industry. This study introduces a novel technique that uses active extracellular substances to induce microalgal cell disruption. A bacterium indigenous to Taiwan, Bacillus thuringiensis, was used to produce the active extracellular substances, which were volatile compounds with high thermal stability. Approximately 74% of fresh microalgal cells were disrupted after a 12-h treatment with the active extracellular substances. Algal lipid extraction efficiency was improved and the oil extraction time was decreased by approximately 37.5% compared with the control treatment. The substances effectively disrupted fresh microalgal cells but not dehydrated microalgal cells. An analysis of microalgal DNA from fresh cells after disruption treatment demonstrated typical DNA laddering, indicating that disruption may have resulted from programmed cell death. This study revealed that biological treatments are environmentally friendly methods for increasing microalgal lipid extraction efficiency, and introduced a microalgal cell self-disruption mechanism.
ABSTRACT
In the present study, evaluation and optimization of taro waste (TW), which was mainly composed of taro peels that contain many starch residues, as the main carbon source in medium were studied. The flask studies showed the optimal medium was using 170g/L of TW which is about 100g/L of glucose and 9g/L of CGM as alternative nitrogen source. Simultaneous saccharification and fermentation (SSF) exhibited higher bioethanol productivity toward separation hydrolysis and fermentation (SHF). The optimal condition of SSF was 5% of Kluyveromyces marxianus K21 inoculum at 40°C resulting in the maximum ethanol concentration (48.98g/L) and productivity (2.23g/L/h) after 22h of cultivation. The scaling up experiment in a 5L bioreactor demonstrated that K21 can still maintain its capability. After 20h of cultivation, 43.78g/L of ethanol (2.19g/L/h of productivity) was achieved corresponding to a 94.2% theoretical ethanol yield.
Subject(s)
Bioreactors , Colocasia/metabolism , Ethanol/metabolism , Fermentation , Kluyveromyces/metabolism , Waste Products , Glucose/metabolism , Hydrolysis , Kluyveromyces/growth & developmentABSTRACT
Pollutant emissions from co-firing of refuse derived fuel (RDF) and coal were investigated in a vortexing fluidized bed combustor (VFBC). RDF-5 was made of common municipal solid waste (MSW). CaCO(3) was injected in the combustor to absorb HCl at 850 degrees C. The results show that NO(x) and HCl emissions increase with RDF-5 co-firing ratio. The NO(x) concentration in flue gas at the bottom of the combustor is higher than that at the top. However, the trend of HCl released is reverse compared with NO(x) emissions. It was found that the HCl concentration decreases with increasing the molar ratio of Ca/Cl. However, the effect of CaCO(3) addition on HCl retention is not significant when the molar ratio of Ca/Cl is higher than 5. The chlorine content in fly ash increases obviously with the molar ratio of Ca/Cl. PCDD/Fs emissions decrease slightly with an addition of CaCO(3). In this study incomplete combustion is regarded as the main cause for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) formation.
