Ethanol production from sweet sorghum juice in repeated-batch fermentation by Saccharomyces cerevisiae immobilized on corncob

Ethanol fermentation from sweet sorghum juice containing 240 g/l of total sugar by Saccharomyces cerevisiae TISTR 5048 and S. cerevisiae NP 01 immobilized on low-cost support materials, corncob pieces, was investigated. In batch fermentation, S. cerevisiae TISTR 5048 immobilized on 6 × 6 × 6 mm³ corncobs gave higher ethanol production than those immobilized on 12 × 12 × 12 mm³ corncobs in terms of ethanol concentration (P), yield (Y _p/s ) and productivity (Q _p ) with the values of 102.39 ± 1.11 g/l, 0.48 ± 0.01 and 2.13 ± 0.02 g/l h, respectively. In repeated-batch fermentation, the yeasts immobilized on the 6 × 6 × 6 mm³ corncobs could be used at least eight successive cycles with the average P, Y _p/s and Q _p of 97.19 ± 5.02 g/l, 0.48 ± 0.02 and 2.02 ± 0.11 g/l h, respectively. Under the same immobilization and repeated-batch fermentation conditions, P (90.75 ± 3.05 g/l) and Q _p (1.89 ± 0.06 g/l h) obtained from S. cerevisiae NP 01 were significantly lower than those from S. cerevisiae TISTR 5048 (P < 0.05), while Y _p/s from both strains were not different. S. cerevisiae TISTR 5048 immobilized on the corncobs also gave significantly higher P, Y _p/s and Q _p than those immobilized on calcium alginate beads (P < 0.05).     

Biodegradation of an aldehyde biocide in rotating biological contactors

Biodegradation of an aldehyde biocide, glutaraldehyde (GA), in a single-stage laboratory-scale rotating biological contactor (RBC) was studied under biocide or organic loadings (OL) of 12–66 g COD m⁻² day⁻¹ and hydraulic retention times (HRT) of 0.6–3.0 h. Biofilms on the RBC were acclimated in 180 ppm GA at a hydraulic loading (HL) of 0.18 m³ m⁻² day⁻¹ and the HRT of 0.60 h. The results showed that under a constant initial chemical oxygen demand (COD) concentration and sufficient mineral salts available, the degree of GA removal in the RBC system was increased with either decreasing OL or increasing HRT. After a period of acclimation, treatment efficiency in terms of GA removal by the RBC receiving GA as a sole carbon source was 89%. The biofilms played an important role in biodegradation of biocide in the RBCs, whereas bio-oxidation of their planktonic counterparts was totally inhibited in the presence of 50 ppm GA. The biochemical oxygen demand (BOD) test could be used as an appropriate analytical procedure for investigating the efficiency of wastewater treatment units when seed was acclimated and had adequate amount.     

A life cycle assessment study of a Canadian post-combustion carbon dioxide capture process system

Purpose

While carbon dioxide capture and storage (CCS) has been widely recognized as a useful technology for mitigating greenhouse gas emissions, it is necessary to evaluate the environmental performance of CCS from a full life cycle perspective to comprehensively understand its environmental impacts. The primary research objective is to conduct a study on life cycle assessment of the post-combustion carbon dioxide capture process based on data from SaskPower’s electricity generation station at the Boundary Dam in Saskatchewan, Canada. A secondary objective of this study is to identify the life cycle impact assessment (LCIA) methodology which is most suitable for the assessment of carbon dioxide capture technology integrated with the power generation system in the Canadian context.

Methods

The study takes a comparative approach by including three scenarios of carbon dioxide capture at the electricity generation station: no carbon dioxide capture (“no capture”), partial capture (“retrofit”), and fully integrated carbon dioxide capture of the entire facility (“capture”). The four LCIA methods of EDIP 97, CML2001, IMPACT2002+, and TRACI are used to convert existing inventory data into environmental impacts. The LCIA results from the four methods are compared and interpreted based on midpoint categories.

Results and discussion

The LCA results showed an increase in the retrofit and capture scenarios compared to the no capture scenario in the impact categories of eutrophication air, ecotoxicity water, ecotoxicity ground surface soil, eutrophication water, human health cancer ground surface soil, human health cancer water, human health noncancer ground surface soil, ozone depletion air, human health noncancer water, and ionizing radiation. The reductions were observed in the retrofit and capture scenarios in the impact categories of acidification, human health criteria air-point source, human health noncancer air, ecotoxicity air, global warming, human health cancer air, and respiratory effects.

Conclusions

Although the four LCIA methodologies significantly differ in terms of reference substances used for individual impact categories, all (TRACI, IMPACT2002+, CML2001, and EDIP 97) showed similar results in all impact categories.     

Ethanol production from sweet sorghum juice using very high gravity technology: Effects of carbon and nitrogen supplementations

Ethanol production from sweet sorghum juice by Saccharomyces cerevisiae NP01 was investigated under very high gravity (VHG) fermentation and various carbon adjuncts and nitrogen sources. When sucrose was used as an adjunct, the sweet sorghum juice containing total sugar of 280 g l⁻¹, 3 g yeast extract l⁻¹ and 5 g peptone l⁻¹ gave the maximum ethanol production efficiency with concentration, productivity and yield of 120.68 ± 0.54 g l⁻¹, 2.01 ± 0.01 g l⁻¹ h⁻¹ and 0.51 ± 0.00 g g⁻¹, respectively. When sugarcane molasses was used as an adjunct, the juice under the same conditions gave the maximum ethanol concentration, productivity and yield with the values of 109.34 ± 0.78 g l⁻¹, 1.52 ± 0.01 g l⁻¹ h⁻¹ and 0.45 ± 0.01 g g⁻¹, respectively. In addition, ammonium sulphate was not suitable for use as a nitrogen supplement in the sweet sorghum juice for ethanol production since it caused the reduction in ethanol concentration and yield for approximately 14% when compared to those of the unsupplemented juices.     

Light acclimation and photoinhibition in threeSpirulina platensis (cyanobacteria) isolates

Three isolates ofSpirulina platensis (Norst) Geitler marked BP, P4P and Z19/2 were compared with respect to their response and acclimation capability to high photon flux densities (HPFD). Cultures exposed to HPFD (1500–3500 mol photon m^–2 s^–1) exhibited a marked decrease in light-dependent O₂ evolution rate. P4P was more sensitive to HPFD than the two other isolates. All three isolates recovered from photoinhibition when placed under low PFD. The BP isolate was able to recover also in the dark but to a lower extent and at a lower rate, while no recovery was observed in the other two isolates under dark conditions. No recovery was observed when protein synthesis was inhibited using chloramphenicol. Cultures grown at 200 mol photon m^–2 s^–1 differed from cultures grown at 120 mol photon m 2 s-1 by their lower maximal photosynthetic rate (P _max ) and higher light saturation (I _k ) value, while being more resistant to HPFD stress. The ability ofSpirulina isolates to acclimate and withstand HPFD may provide useful information for the selection of strains useful for outdoor mass cultivation.Author for correspondence     

Ethanol production from sweet sorghum juice in batch and fed-batch fermentations by <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

Sweet sorghum juice supplemented with 0.5% ammonium sulphate was used as a substrate for ethanol production by Saccharomyces cerevisiae TISTR 5048. In batch fermentation, kinetic parameters for ethanol production depended on initial cell and sugar concentrations. The optimum initial cell and sugar concentrations in the batch fermentation were 1 × 10⁸ cells ml⁻¹ and 24 °Bx respectively. At these conditions, ethanol concentration produced (P), yield (Y _ps) and productivity (Q _p ) were 100 g l⁻¹, 0.42 g g⁻¹ and 1.67 g l⁻¹ h⁻¹ respectively. In fed-batch fermentation, the optimum substrate feeding strategy for ethanol production at the initial sugar concentration of 24 °Bx was one-time substrate feeding, where P, Y _ps and Q _p were 120 g l⁻¹, 0.48 g g⁻¹ and 1.11 g l⁻¹ h⁻¹ respectively. These findings suggest that fed-batch fermentation improves the efficiency of ethanol production in terms of ethanol concentration and product yield.     

Acid hydrolysis of sugarcane bagasse for lactic acid production

In order to use sugarcane bagasse as a substrate for lactic acid production, optimum conditions for acid hydrolysis of the bagasse were investigated. After lignin extraction, the conditions were varied in terms of hydrochloric (HCl) or sulfuric (H₂SO₄) concentration (0.5–5%, v/v), reaction time (1–5 h) and incubation temperature (90–120 °C). The maximum catalytic efficiency (E) was 10.85 under the conditions of 0.5% of HCl at 100 °C for 5 h, which the main components (in g l⁻¹) in the hydrolysate were glucose, 1.50; xylose, 22.59; arabinose, 1.29; acetic acid, 0.15 and furfural, 1.19. To increase yield of lactic acid production from the hydrolysate by Lactococcus lactis IO-1, the hydrolysate was detoxified through amberlite and supplemented with 7 g l⁻¹ of xylose and 7 g l⁻¹ of yeast extract. The main products (in g l⁻¹) of the fermentation were lactic acid, 10.85; acetic acid, 7.87; formic acid, 6.04 and ethanol, 5.24.