120 research outputs found
Supplemental material for Physicochemical characterization of three natural clays used as adsorbent for the humic acid removal from aqueous solution
No full textSupplemental Material for Physicochemical characterization of three natural clays used as adsorbent for the humic acid removal from aqueous solution by Soumahoro Gueu, Gisèle Finqueneisel, Thierry Zimny, Danièle Bartier and Benjamin Kouassi Yao in Adsorption Science & Technology</p
Exploring the Synthesis of Lactic Acid from Sugarcane Molasses Collected in Côte d’Ivoire Using Limosilactobacillus fermentum ATCC 9338 in a Batch Fermentation Process
No full textLactic acid (LA) is a high-value chemical with growing demand for the production of polymers and plastics and in the food and pharmaceutical industries. However, production costs remain a significant constraint when using conventional food-grade substrates. This study investigates Ivorian sugarcane molasses, an abundant agro-industrial by-product, as a low-cost carbon source for LA production via batch fermentation with Limosilactobacillus fermentum ATCC 9338. Molasses was pretreated by acid hydrolysis to improve fermentability, increasing glucose and fructose concentrations. Comparative fermentations using raw and pretreated molasses showed a 75% increase in LA production (32.4 ± 0.03 g/L) after pretreatment. Optimisation using Box–Behnken design revealed that the initial sugar concentration, inoculation rate, and stirring speed significantly influenced lactic acid production.
Under optimal conditions, a maximum LA concentration of 52.4 ± 0.49 g/L was achieved with a yield of 0.95 g/g and productivity of 0.73 g/L·h. Kinetic analysis confirmed efficient sugar utilisation under the optimised conditions, and polarimetry revealed a near-racemic lactic acid. A simplified cost analysis showed that molasses could reduce carbon source costs by over 70% compared to refined sugars, supporting its economic viability. This work demonstrates the potential of pretreated molasses under robust fermentation conditions as a sustainable and cost-effective substrate for LA production in resource-limited contexts. The approach aligns with circular bioeconomy principles and presents a replicable model for decentralised bioproduction in a developing country like Côte d’Ivoire
A green and optimized approach for lactic acid recovery from fermented molasses using n ‐butanol for local industrial applications in Côte d’Ivoire
No full textThis study reports the development and optimization of a sustainable, cost-effective
process for recovering lactic acid from fermented molasses using n-butanol
as the extraction solvent. Successful extraction was confirmed by nuclear magnetic resonance (NMR) spectroscopy, which demonstrated the presence of monomeric and dimeric lactic acid with minimal impurities. Enantiomeric analysis revealed a near-racemic mixture (51.4% d-lactic acid and 48.6% l-lactic acid), highlighting the heterofermentative nature of the strain, and this composition remained stable even after 6 months. Racemic lactic acid can be exploited for the synthesis of amorphous poly(lactic acid), a preferred candidate for the production of biodegradable materials, drug delivery vehicles, and low-strength scaffolding material for tissue regeneration. This would expand the potential applications of the product in the pharmaceutical,
biomedical, and cosmetic industries. The extraction process was optimized through response surface methodology (RSM), identifying ammonium sulfate concentration, solvent-to-broth ratio, and pH as significant parameters influencing recovery. The quadratic model exhibited strong predictive performance (R2 = 0.9996) with no significant lack of fit, validating the reliability of the model. Optimal conditions (57.5%
ammonium sulfate, solvent-to- broth ratio of 4.12, and pH 1.24) improved lactic acid recovery. These findings contribute to the valorization of local agro-industrial
waste, promoting greener biotechnological processes, and providing a scalable approach to high-value products in Côte d’Ivoire, aligning with the nation’s goals of sustainable development and circular economy
Synchronous Byzantine Broadcast algorithms for a dishonest majority
No full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (page 37).Deterministic Byzantine Broadcast requires f+1 rounds for any f malicious processes, in the synchronous, authenticated setting. In the non-deterministic case, Katz and Koo [2] showed a lower-bound of [omega](2n=(n-f)) rounds, but it remains an open question whether the bound is tight, specically when f >/= n/2 (a dishonest majority). This thesis explores ways to improve the eciency of Byzantine Broadcast algorithms for a dishonest majority. In particular, we present an expected 10 round protocol for f = n/2, which works by constructing a hierarchy of quorums, to gather as many signatures as possible, before commitment. Finally, we offer brief commentary on how similar techniques could extend to f > n/2.by Benjamin Yao Chan.M. Eng.M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Scienc
Modeling and Optimization of M-cresol Isopropylation for Obtaining N-thymol: Combining a Hybrid Artificial Neural Network with a Genetic Algorithm
Get PDFThe application of a hybrid framework based on the combination, artificial neural network-genetic algorithm (ANN-GA), for n-thymol synthesis modeling and optimization has been developed. The effects of molar ratio propylene/cresol (X1), catalyst mass (X2) and temperature (X3) on n-thymol selectivity Y1 and m-cresol conversion Y2 were studied. A 3-8-2 ANN model was found to be very suitable for reaction modeling. The multiobjective optimization, led to optimal operating conditions (0.55 ≤X1≤0.77; 1.773 g ≤ X2 ≤1.86 g; 289.74 °C ≤ X3 ≤291.33 °C) representing good solutions for obtaining high n-thymol selectivity and high m-cresol conversion. This optimal zone corresponded to n-thymol selectivity and m-cresol conversion ranging respectively in the interval [79.3; 79.5]% and [13.4 %; 23.7]%. These results were better than those obtained with a sequential method based on experimental design for which, optimum conditions led to n-thymol selectivity and m-cresol conversion values respectively equal to 67%and 11%. The hybrid method ANN-GA showed its ability to solve complex problems with a good fitting
Negative extreme events in gross primary productivity and their drivers in China during the past three decades
Get PDFThis is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Climate extremes have remarkable impacts on ecosystems and are expected to increase with future global warming. However, only few studies have focused on the ecological extreme events and their drivers in China. In this study, we carried out an analysis of negative extreme events in gross primary productivity (GPP)in China and the sub-regions during 1982–2015, using monthly GPP simulated by 12 process-based models (TRENDYv6)and an observation-based model (Yao-GPP). Extremes were defined as the negative 5th percentile of GPP anomalies, which were further merged into individual extreme events using a three-dimensional contiguous algorithm. Spatio-temporal patterns of negative GPP anomalies were analyzed by taking the 1000 largest extreme events into consideration. Results showed that the effects of extreme events decreased annual GPP by 2.8% (i.e. 208 TgC year−1)in TRENDY models and 2.3% (i.e. 151 TgC year−1)in Yao-GPP. Hotspots of extreme GPP deficits were mainly observed in North China (−53 gC m−2 year−1)in TRENDY models and Northeast China (−42 gC m−2 year−1)in Yao-GPP. For China as a whole, attribution analyses suggested that extreme low precipitation was associated with 40%–50% of extreme negative GPP events. Most events in northern and western China could be explained by meteorological droughts (i.e. low precipitation)while GPP extreme events in southern China were more associated with temperature extremes, in particular with cold spells. GPP was revealed to be much more sensitive to heat/drought than to cold/wet extreme events. Combined with projected changes in climate extremes in China, GPP negative anomalies caused by drought events in northern China and by temperature extremes in southern China might be more prominent in the future.Natural Science Foundation for Distinguished Young Scholars of Hubei Province of ChinaNational Natural Science Foundation of China111 ProjectChina Scholarship CouncilSwiss National Science Foundatio
Erratum:Author Correction: How to probe the spin contribution to momentum relaxation in topological insulators (Nature communications (2018) 9 1 (56))
No full textThe original version of this Article contained an error in the spelling of the author Benjamin H. Williams, which was incorrectly given as Benjamin H. Willams. This has now been corrected in both the PDF and HTML versions of the Article.</p
Valorisation des déchets d’agroressources par bioproduction d’acide citrique
No full textNational audienceA study on the production of citric acid from various fruit and starch wastes was performed for their potential valorization. The results obtained for the fruits show that the pulp of the papaya (Carica papaya), the passion fruit (Passiflora edulis) and the mirabelle fruit (Prunus domestica) gave the best ratios of the citric acid contents on the quantity of total sugars consumed with respective values of 0.58; 0.63 and 0.77 and respectively produced citric acid amounts of 72.5; 91, 3 and 61.6 g/kg. For starchy foods, sweet potato peels (Ipomoea batatas) had the best citric acid production and the best ratio of the citric acid contents on the quantity of total sugars consumed with respective values of 16.7g / kg and 0.28g. In general, the citric acid contents, lower than 50 g/kg during the first three days of fermentation evolve to values of 100-287 g/kg on the twelfth day. The study of the Hydrogen potential variation shows that it decreases rapidly during the various wastes fermentation.Une étude sur la production d’acide citrique à partir de divers déchets de fruits et d’amylacés a été entreprise pour leurs potentielles valorisations. Les résultats obtenus pour les fruits montrent que les pulpes de la papaye (Carica papaya), du fruit de la passion (Passiflora edulis) et de la mirabelle (Prunus domestica) donnent les meilleurs rapports des teneurs en acide citrique sur la quantité de sucres totaux consommés avec des valeurs respectives de 0,58 ; 0,63 et 0,77 ainsi que des quantités d’acide citrique produites respectives de 72,5 ; 91, 3 et 61,6 g/kg. Pour les amylacés, l’épluchure de la patate douce (Ipomoea batatas) présente la meilleure production d’acide citrique et le meilleur rapport des teneurs en acide citrique sur la quantité de sucres totaux consommés avec des valeurs respectives de 16,7 g/kg et 0,28. De façon générale, les teneurs en acide citrique, inférieurs à 50g/kg pendant les trois premiers jours de fermentation évoluent vers des valeurs de 100-287 g/kg au douzième jour. L’étude de la variation du potentiel Hydrogène montre qu’il décroit rapidement au cours de la fermentation des différents déchets
Transesterification of Crude Rubber Oil Catalyzed by Lipase Extract Powder of Germinated Rubber Kernels for Biodiesel Production
No full textLipases are essential in many industrial processes. Although microbial lipases are widely used, plant lipases remain more accessible and abundant, particularly in germinated kernels. This study aims to evaluate the catalytic potential of lipase extract powder of germinated rubber kernels in transesterification reaction. Germinated rubber kernels, lipase extract powder of germinated rubber kernels, and crude oils of palm (PKO), Jatropha curcas (JCO), and rubber (RSO) were characterized. The presence of lipase in the plant extract powder was evidenced by FT-IR and SEM-EDX analyses and hydrolysis reaction. Biodiesel was produced from crude rubber oil. The results showed that germinated rubber kernels have high moisture (33.48%), protein (15.75%), and fat (50.11%) contents. The optimum hydrolytic activities of lipase on PKO, JCO, and RSO were 25.67 U/mL, 26.67 U/mL, and 31 U/mL, respectively, at pH 5. Lipase extract concentration, temperature, and storage time influenced the lipase hydrolytic activity. The optimum biodiesel yield (29.63%) was obtained at 30 °C. The addition of co-solvents (water and n-hexane) to the reaction mixture increased yields from 20.47% (without co-solvent) to 31.06% and 21.85%, respectively. These insights show that germinated rubber seeds are rich in oil and contain lipase with good hydrolytic and catalytic activity
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