Amylolysis is predominated by cell-surface-bound hydrolase during anaerobic fermentation under mesophilic conditions.

While knowing the amylolysis mechanism is important to effectively decompose corn starch fed into an anaerobic digestor, the objective of this study was to detect the activities and locations of α-amylase in a continuous reactor and batch cultures. In the continuous reactor operated at 35 °C, the greatest cell-bound α-amylase activity was found to be 4.7 CU mL-1 at hydraulic retention time (HRT) = 9 h, while the greatest volumetric hydrogen production rate (rH2) was observed at HRT = 3 h as 61 mmol L-1 day-1. In the batch tests, the cell-bound α-amylase activities increased when the carbohydrate concentration decreased, and no significant reducing sugar accumulation was found in the serum bottles. By examining the specific hydrogen production rate (qH2) against different corn starch concentrations, the half-saturation constant (KSta) and the maximum qH2 were regressed to be 0.47 g L-1 and 6 mmol g-VSS-1 d-1, respectively. The electronic microscopic images showed that the microbes could colonize on the starch granules without the disturbance of any floc-like materials. Conclusively, by excluding the methanogens and floc matrix, the secreted α-amylases are predominately bound on the cell surfaces and enabled the microbial cells favorably attach on large substrates for hydrolysis under the mesophilic condition.

A metabolic-activity-detecting approach to life detection: Restoring a chemostat from stop-feeding using a rapid bioactivity assay.

A mediated glassy carbon electrode covered by a thin-film polyviologen was used in the present study to rapidly detect bioactivity in a mixed-culture chemostat (dominated by Clostridium sp.). With the addition of 1mM hexacyanoferrate and 9mM glucose, the current increasing rate (dI/dt) measured under a poised potential of 500mV (vs. Ag/AgCl) can be defined as the quantity of metabolic activity. In the experiment of restoring the chemostat from stop-feeding, it is suggested that when the dI/dt was >2µAmin-1, the influent pump could be directly turned on to maintain the high dilution rate of 0.5h-1; when the dI/dt was lower than 2µAmin-1, reducing the dilution rate would be needed to avoid cell wash out. Since the soluble mediators and polyviologen film will enhance performances by favorable electron transfer and positively charged surfaces, respectively, we suggest that the method can also be employed to detect the bioactivities in environmental samples.

Active extracellular substances of Bacillus thuringiensis ITRI-G1 induce microalgae self-disruption for microalgal biofuel.

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.

Bamboo saccharification through cellulose solvent-based biomass pretreatment followed by enzymatic hydrolysis at ultra-low cellulase loadings.

The modified cellulose solvent- (concentrated phosphoric acid) and organic solvent- (95% ethanol) based lignocellulose fractionation (COSLIF) was applied to a naturally-dry moso bamboo sample. The biomass dissolution conditions were 50 degrees C, 1 atm for 60 min. Glucan digestibility was 88.2% at an ultra-low cellulase loading of one filter paper unit per gram of glucan. The overall glucose and xylose yields were 86.0% and 82.6%, respectively. COSLIF efficiently destructed bamboo's fibril structure, resulting in a approximately 33-fold increase in cellulose accessibility to cellulase (CAC) from 0.27 to 9.14 m(2) per gram of biomass. Cost analysis indicated that a 15-fold decrease in use of costly cellulase would be of importance to decrease overall costs of biomass saccharification when cellulase costs are higher than $0.15 per gallon of cellulosic ethanol.

Cellulosic hydrogen production with a sequencing bacterial hydrolysis and dark fermentation strategy.

In this study, cellulose hydrolysis activity of two mixed bacterial consortia (NS and QS) was investigated. Combination of NS culture and BHM medium exhibited better hydrolytic activity under the optimal condition of 35 degrees C, initial pH 7.0, and 100rpm agitation. The NS culture could hydrolyze carboxymethyl cellulose (CMC), rice husk, bagasse and filter paper, among which CMC gave the best hydrolysis performance. The CMC hydrolysis efficiency increased with increasing CMC concentration from 5 to 50g/l. With a CMC concentration of 10g/l, the total reducing sugar (RS) production and the RS producing rate reached 5531.0mg/l and 92.9mg/l/h, respectively. Furthermore, seven H2-producing bacterial isolates (mainly Clostridium species) were used to convert the cellulose hydrolysate into H2 energy. With an initial RS concentration of 0.8g/l, the H2 production and yield was approximately 23.8ml/l and 1.21mmol H2/g RS (0.097mmol H2/g cellulose), respectively.