Yanling Yu

Degradation of raw corn stover powder (RCSP) by an enriched microbial consortium and its community structure.

A microbial consortium with a high cellulolytic activity was enriched to degrade raw corn stover powder (RCSP). This consortium degraded more than 51% of non-sterilized RCSP or 81% of non-sterilized filter paper within 8 days at 40°C under facultative anoxic conditions. Cellulosome-like structures were observed in scanning electron micrographs (SEM) of RCSP degradation residue. The high cellulolytic activity was maintained during 40 subcultures in a medium containing cellulosic substrate. Small ribosomal gene sequence analyses showed the consortium contains uncultured and cultured bacteria with or without cellulolytic activities. Among these bacteria, some are anaerobic others aerobic. Analyses of the culture filtrate showed a typical anoxic polysaccharide fermentation during the culturing process. Reducing sugar concentration increased at early stage followed by various fermentation products that were consumed at the late stage.

Onsite bio-detoxification of steam-exploded corn stover for cellulosic ethanol production.

In the process of ethanol production from steam-exploded corn stover (SECS), a cellulose-degradation strain of Aspergillus nidulans (FLZ10) was investigated whether it could remove the inhibitors released from steam exploded pretreatment , and thereby be used for biological detoxification on Saccharomycescerevisiae. The results showed that FLZ10 removed 75.2% formic acid, 53.6% acetic acid, and 100% hydroxymethyl furfural (5-HMF) and furfural from the hydrolysate washed from SECS after 72h cultivation. A cellulase activity of 0.49 IU/ml was simultaneously produced while the biological detoxification occurred. An ethanol yield of 0.45 g/g on glucose was obtained in the hydrolysate biodetoxified by FLZ10. The glucose consumption rate of FLZ10 was much lower than that of S. cerevisiae, thereby it had little competition with S. cerevisiae on glucose consumption. Based on SECS to ethanol mass balance analysis, with the onsite bio-detoxification, fermentation using S. cerevisiae effectively converted monomeric glucose with 94.4% ethanol yield.

Factors affecting microalgae harvesting efficiencies using electrocoagulation-flotation for lipid extraction

Microalgae harvesting is a relatively costly process in microalgae biodiesel production. In this study, electrocoagulation-flotation (ECF) was employed to harvest microalgae (Chlorella vulgaris). Higher current density achieved higher collection efficiency, but also resulted in higher energy consumption and increased levels of dissolved aluminium. At the same ratio of current density to initial cell density, collection efficiency decreased from 99.0% of 0.24 g L−1 to 30.5% of 1.17 g L−1 when the electrolysis time was 20 min. For stirring and aeration, the highest collection efficiency was 98.4%, obtained by stirring at 50 rpm for 20 min. This efficiency was nearly equal to the highest collection efficiency for aeration: 98.3% for 50 mL min−1 aeration at 30 min. Acidic and neutral culture conditions were beneficial due to the positively charged aluminium species in the culture; higher collection efficiencies (more than 98%) occurred with pH levels of 5–7 after 20 min. The lowest energy consumption of 0.61 kW h kg−1 was achieved at pH 5. In this research, ECF exhibited higher collection efficiency (99.4%) as compared to the 93.5% collection efficiency of chemical flocculation (Al2(SO4)3).

Effects of drying pretreatment and particle size adjustment on the composting process of discarded flue-cured tobacco leaves:

The main characteristic of discarded flue-cured tobacco leaves is their high nicotine content. Aerobic composting is an effective method to decrease the nicotine level in tobacco leaves and stabilize tobacco wastes. However, high levels of nicotine in discarded flue-cured tobacco leaves complicate tobacco waste composting. This work proposes a drying pretreatment process to reduce the nicotine content in discarded flue-cured tobacco leaves and thus enhance its carbon-to-nitrogen ratio to a suitable level for composting. The effect of another pretreatment method, particle size adjustment, on composting efficiency was also tested in this work. The results indicated that the air-dried (nicotine content: 1.35%) and relatively long discarded flue-cured tobacco leaves (25 mm) had a higher composting efficiency than damp (nicotine content: 1.57%) and short discarded flue-cured tobacco leaves (15 mm). When dry/25 mm discarded flue-cured tobacco leaves mixed with tobacco stems in an 8:2 ratio was composted at a temperature above 55 °C for 9 days, the nicotine content dropped from 1.29% to 0.28%. Since the discarded flue-cured tobacco leaves was successfully composted to a fertile and harmless material, the germination index values increased to 85.2%. The drying pretreatment and particle size adjustment offered ideal physical and chemical conditions to support microbial growth and bioactivity during the composting process, resulting in efficient conversion of discarded flue-cured tobacco leaves into a high quality and mature compost.

Simultaneous algae-polluted water treatment and electricity generation using a biocathode-coupled electrocoagulation cell (bio-ECC)

How to utilize electrocoagulation (EC) technology for algae-polluted water treatment in an energy-efficient manner remains a critical challenge for its widespread application. Herein, a novel biocathode-coupled electrocoagulation cell (bio-ECC) with sacrificial iron anode and nitrifying biocathode was developed. Under different solution conductivities (2.33±0.25mScm-1 and 4.94±0.55mScm-1), the bio-ECC achieved almost complete removal of algae cells. The maximum power densities of 8.41 and 11.33Wm-3 at corresponding current densities of 48.03Am-3 and 66.26Am-3 were obtained, with the positive energy balance of 4.52 and 7.44Wm-3. In addition, the bio-ECC exhibited excellent NH4+-N removal performance with the nitrogen removal rates of 7.28mgL-1h-1 and 6.77mgL-1h-1 in cathode chamber, indicating the superiority of bio-ECC in NH4+-N removal. Pyrosequencing revealed that nitrifiers including Nitrospira, Nitrobacter, Nitrosococcus, and Nitrosomonas were enriched in biocathode. The removal mechanisms of algae in anode chamber were also explored by AFM and SEM-EDX tests. These results provide a proof-of-concept study of transferring energy-intensive EC process into an energy-neutral process with high-efficiency algae removal and electricity recovery.