Biotechnological potential of Zymotis-2 bioreactor for the cultivation of filamentous fungi.

BACKGROUND/AIM: A new prototype of Solid-State Fermentation Bioreactor, namely "Zymotis-2 ", was developed to produce fungal spores. MAIN METHODS AND MAJOR RESULTS: A fermentation process for fungal spores, and hydrolase enzymes (endo and exoglucanases, amylases) production by Trichoderma asperellum DWG3, Aspergillus niger G131 and Beauveria bassiana was scaled-up from flasks and glass Raimbault column packed with 20 g of solid substrates (dry weight) to 5 kg of solid substrate by using the new Zymotis-2 bioreactor. Fungi strains growth using a mix of vine shoots, wheat bran, and olive pomace was tested under similar experimental conditions in Zymotis-2 bioreactor, column bioreactor and flasks in a parallel fermentation system. Overall, significant spore production on Zymotis-2 bioreactor was obtained, achieving 22.01 ± 0.01×109 spores/g DM 16.30 ± 0.07 × 109 spores/g DM, and 3.30 ± 0.07 × 109 spores/g DM for B. bassiana, T. asperellum DWG3, and A. niger G131, respectively. Forced aeration increased the endoglucanases, exoglucanases and amylases activities for T. asperellum DWG3 but B. bassiana and A. niger G131 were affected negatively by the aerated process, showing the lowest enzyme activities. CONCLUSIONS AND IMPLICATIONS: In conclusion, a high yield of spores was obtained at 137 h of cultivation time, confirming the validity of the new Zymotis-2 bioreactor to produce virulent spores at low cost by T. asperellum, B. bassiana and A. niger G131.

Predicting attenuation of solar radiation (UV-B, UV-A and PAR) in waste stabilization ponds under Sahelian climatic conditions.

Because of its importance in pathogen removal and algal productivity in waste stabilization ponds, sunlight penetration was measured in microcosms and in situ under Sahelian climatic conditions. The different wavelengths were detected using a submersible radiometer equipped with three sensors: UV-B (311 nm), UV-A (369 nm) and photosynthetically available radiation (PAR, 400-700 nm). UV-B was more attenuated than UV-A and PAR. Facultative pond was more light-attenuating than maturation pond. The mean euphotic depths for UV-B were 0.20 and 0.31 m, respectively, in the facultative and maturation ponds; PAR penetrated deeper with mean euphotic depths of 0.27 and 0.42 m, respectively. The mean Secchi depths were 0.16 and 0.10 m in the maturation and facultative ponds waters, respectively. In view of the reported results, the contribution of the deeper sections of ponds to pathogen removal mediated by sunlight seems negligible. Therefore, when designing WSPs, these findings should be considered to increase the penetration of damaging wavelengths in order to ensure efficient microbial removal. For more pathogen elimination, downstream shallow ponds could be considered. The paper also shows how suspended solids, turbidity, and Secchi depth are related to the attenuation coefficients and euphotic depths. The developed models could be used to predict light penetration and then algal growth and pathogen removal mediated by sunlight in waste stabilization ponds located in Sahelian climate.

Effect of post-treatment conditions on the inactivation of helminth eggs (Ascaris suum) after the composting process.

Safe and appropriate disposal of human waste is a basic requirement for sanitation and protection of public health. For proper sanitation and nutrient recovery, it is necessary to ensure effective treatment methods to complete pathogen destruction in excreta prior to reuse. Composting toilets convert faeces to a reusable resource such as fertilizer or humus for organic agriculture. A composting toilet for rural Burkina Faso was created by modifying a commercial model available in Japan to improve hygiene and increase food production. The toilet has shown to result in a degraded final product, but its effectiveness for pathogen destruction was unclear due to low temperatures generated from the toilet. This study aimed to sanitize compost withdrawn from the composting toilet for food production by setting post-treatment conditions. The inactivation kinetics of Ascaris suum eggs, selected as an indicator for helminth eggs, was determined during post-treatment at different temperatures (30°C, 40°C, 50°C and 60°C) with varying moisture contents (MC) (50%, 60% and 70%). The treatment of compost in a possible additional post-treatment after the composting process was tried in the laboratory test. Inactivation of A. suum eggs was fast with greater than two log reductions achieved within 2 h for temperature 50°C and 50% MC and greater than three log reductions for temperature 60°C and 50% MC within 3 h. Statistical analysis showed the significant impact of temperature and moisture on the inactivation rates of A. suum eggs. The post-treatment can efficiently increase helminth eggs destruction prior to reuse.

The impact of pond depth and environmental conditions on sunlight inactivation of Escherichia coli and enterococci in wastewater in a warm climate.

Microcosm experiments were carried out under dark and real sunlight conditions in Ouagadougou (Burkina Faso) to investigate the survival of faecal indicators (Escherichia coli and enterococci) in secondary wastewater. Light damage was estimated by loss of bacterial culturability. The results clearly show that sunlight has a deleterious effect on the survival of both indicators. The mean dark inactivation coefficients for E. coli and enterococci were 0.045 and 0.047 h(-1), respectively, whereas inactivation coefficients in the shallowest microcosm (0.1 m) in illuminated conditions were 0.796 and 0.559 h(-1), respectively. No significant effect of pond depth (0.1-0.9 m) on the inactivation of both indicators was observed in the dark. However, the effect of depth was significant in the microcosms exposed to sunlight, probably because of attenuation. In illuminated conditions, enterococci were broadly inactivated more rapidly than E. coli (T90 = 26.81 h for E. coli and 15.67 h for enterococci in the 0.4 m microcosm). However, E. coli presented greater variability in the survival capabilities, suggesting difficulties in interpreting data using only E. coli as an indicator. Therefore, the use of both indicators together should be advisable for the assessment of effluent quality from waste stabilization ponds in the Sahelian region.

Sunlight inactivation of Escherichia coli in waste stabilization microcosms in a sahelian region (Ouagadougou, Burkina Faso).

Experiments on sunlight inactivation of Escherichia coli were conducted from November 2006 to June 2007 in eight outdoors microcosms with different depths filled with maturation pond wastewater in order to determine pond depth influence on sunlight inactivation of E. coli. The long-term aim was to maximize sunlight inactivation of waterborne pathogens in waste stabilization ponds (WSPs) in sahelian regions where number of sunny days enable longer exposure of wastewater to sunlight. The inactivation was followed during daylight from 8.00 h to 17.00 h and during the night. Sunlight inactivation rates (K(S)), as a function of cumulative global solar radiation (insolation), were 16 and 24 times higher than the corresponding dark inactivation (K(D)) rates, respectively in cold and warm season. In warm season, E. coli was inactivated far more rapidly. Inactivation of E. coli follows the evolution of radiation during the day. In shallow depth microcosms, E. coli was inactivated far more rapidly than in high depth microcosms. The physical chemical parameters [pH, dissolved oxygen (DO)] of microcosms water were higher in shallow depth microcosms than in high depth microcosms suggesting a synergistic effect of sunlight and these parameters to damage E. coli. To increase the efficiency of the elimination of waterborne bacteria, the use of maturation ponds with intermediate depths (0.4m) would be advisable in view of the high temperatures and thus evaporation recorded in sahelian regions.