Abstract This paper investigates the use of machine learning (ML) techniques to study the effect of different process conditions on ethanol production from lignocellulosic sugarcane bagasse biomass using S. cerevisiae in a simultaneous hydrolysis and fermentation (SHF) process. The effects of temperature, enzyme concentration, biomass load, inoculum size and time were investigated using artificial neural networks, a C5.0 classification tree and random forest algorithms. The optimization of ethanol production was also evaluated. The results clearly depict that ML techniques can be used to evaluate the SHF (R2 between actual and model predictions higher than 0.90, absolute average deviation lower than 8.1% and RMSE lower than 0.80) and predict optimized conditions which are in close agreement with those found experimentally. Optimal conditions were found to be a temperature of 35 ºC, an SHF time of 36 h, enzymatic load of 99.8%, inoculum size of 29.5 g/L and bagasse concentration of 24.9%. The ethanol concentration and volumetric productivity for these conditions were 12.1 g/L and 0.336 g/L.h, respectively.

Abstract This study evaluated the effects of aeration (constant aeration, intermittent aeration and a lack of aeration) and hydraulic retention time (HRT) (2, 3 and 4 days) on a continuous process with cell recycling, using chitosan as a natural coagulant for the sedimentation of a C1 mixed culture. This culture was used for the biodegradation of hydrocarbons present in the effluent contaminated with diesel oil and gasoline. The responses monitored included the turbidity removal (TR), total petroleum hydrocarbon (TPH) removal and volatile suspended solids (VSS). Constant aeration and an HRT of 4 days produced the best results for the continuous process, resulting in the highest TPH removals (94% and 75% reductions in the supernatant and reaction tank, respectively) and TR (95%).

Abstract Asymmetric alumina hollow fibres produced by the phase inversion/sintering method present advantages in that high area/volume ratios and low mass transfer resistances are achieved due to the geometric configuration and the pore size distribution, respectively. Here we characterise hollow fibres that were prepared with different internal coagulants and at different sintering temperatures. Additionally, a palladium membrane was deposited on these different hollow fibres and hydrogen permeabilities through them were compared. More fingers were obtained when a mixture of solvent with water was used as internal coagulant, instead of pure water. At the same sintering temperature, nitrogen permeance through the fibre was increased 5-fold when a mixture of solvent and water was used as internal coagulant instead of pure solvent, and the water flux was increased 7-fold. The decrease in the sintering temperature increased the water permeance through the fibre from 21.4 to 63.9 L h-1 m-2 kPa-1, but decreased its mechanical strength from 74 to 41 MPa. The hydrogen permeance at 450 °C was increased from 5.54x10-5 to 3.06 x10-3 mol m-2 s-1 kPa-1 when using a more permeable hollow fibre as substrate. These results elucidate better conditions to fabricate hollow fibres that present low mass transfer resistances.

AbstractBiosurfactants have a wide range of applications in emulsions, separations, and solubilization because these chemicals reduce the surface tension and viscosity of solutions. This work studied rhamnolipid production using a batch bioreactor with a working volume of 1.5 liters, Pseudomonas aeruginosa ATCC (American Type Culture Collection) 10145 strain, and the greasy effluent from the slaughter of poultry and pigs as the substrate. The main goal of this research was to evaluate the level of aeration, agitation speed and inoculum concentration using a Central Composite Design (CCD). Experimental conditions were selected using the surface response technique obtained from the CCD, and the results were validated to test the reproducibility. The following operating conditions were selected: 1.2 vvm level of aeration, 600 rpm agitation speed, and 1.0 g/L biomass inoculum concentration. Under these conditions, the following results were obtained: the rhamnose production, surface tension and emulsifying index were 5.37 g/L, 25.6 dyne/cm and 100%, respectively.

An analysis was made of the use of whey fermentation by Lactobacillus acidophilus LA-5 for encapsulated probiotic bacteria cell production. Fermentation was done in a 2-liter Biostat B Fermentor at 28±1 ºC without air supply and agitation maintained at 200 rpm. Different processing conditions were studied using Center Composite Design applied to Surface Response Methodology. Maximum cell yield (2.7 x10(10) NMP/mL for 36 hours) was achieved with 30.85 g/L of lactose, a pH value of 6.45 and 1.04 g/L of inoculum. Cell growth was evaluated using reconstituted and fresh whey after 144 hours of fermentation in pre-optimized conditions. Cell concentration after fermentation was 10(10) MPN/mL in all the assays. The Verhulst model proved to be satisfactory to fit the experimental results, providing a stationary cell concentration of 6.0 g/L and a specific growth rate of 0.09 h-1. Cells were collected by centrifugation at 15000g for 5 minutes at 4 ºC, immobilized in 2% alginate, and dried to a constant weight at 50 ºC. Immobilized probiotic cells presented 10(11) MPN/g, a time required to kill 90% of the organisms (D value) of 18 h (70 ºC), an activation energy of 76.04 kJ/mol for thermal inactivation, and an in vitro resistance to low pH (D value of 62.5 min at 37 ºC, pH 2.5).

The immobilization of Aspergillus oryzae β-galactosidase was achieved by entrapment in sodium alginate and gelatin and cross-linking with glutaraldehyde. The optimal concentrations of the aforementioned variables in the immobilization process were determined using an orthogonal central composite design with an orthogonal axial value of 1.35313. The concentrations of alginate, gelatin and glutaraldehyde that provided the greatest enzymatic activity were 6.60%, 4.05% and 3.64% (w/v), respectively. The stability of the immobilized enzyme under the optimal conditions was evaluated through daily activity assays. After 25 uses, a 20% decrease in the enzymatic activity was observed, indicating that the immobilization process could be used to produce a stable biocatalyst. This study investigates the influence of lactose and product concentrations on kinetic reaction hydrolysis. The concentration ranges for the studied variables were 10 to 56 g/L for lactose and 0 to 11.5 g/L for glucose and galactose. Only galactose presented a competitive inhibitory effect.

The anaerobic treatment of wastewater from the household and personal products industry was studied using a 16.3 L hybrid reactor (UASB and biofilter). The top of the UASB reactor was filled with coconut shells to act as the support material for the biofilter. The wastewater was characterized in terms of pH (1.0 - 12.0), COD (1,000 - 5,000 mg/L), BOD5 (700 - 1,500 mg/L), chloride (55 - 850 mg/L), ammonia nitrogen (0.4 - 0.9 mg/L), total Kjeldahl nitrogen (22.1 - 34.0 mg/L), phosphorus (2.0 - 2.5 mg/L), anionic surfactants (100 - 600 mg/L), turbidity (115 - 300 NTU) and total suspended solids (450 - 1,440 mg/L). The bioreactor was operated continuously for 120 days at room temperature (26 ± 5ºC) with hydraulic retention times of 50, 40 and 60 h. COD and BOD removals and biogas production were evaluated in order to analyze process efficiency. The average removal efficiencies for COD (77%, 72% and 80%) and BOD5 (approximately 90%) were obtained with HRTs of 50, 40 and 60 h, respectively. The average specific biogas production was 0.32 L/g COD (at standard temperature and pressure) for the three experimental runs. These data indicate good reactor efficiency and suggest the possibility of using this system to treat wastewater generated by the household and personal products industry.