Feeding Rate Of Glycerol Research Articles

Koopman modeling and optimal control for microbial fed-batch fermentation with switching operators

The modeling of microbial fed-batch fermentation with switching operators to product 1,3-propanediol (1,3-PD) still maintains a challenge because it is strongly of nonlinearity and uncertainty. Machine learning methods for learning such models have become a hot research topic, but the interpretability of existing techniques remains a challenging problem. Recently, the Koopman operator, which is a linear operator governing the eigenfunction evolution along trajectories of a nonlinear dynamical system with switching operators, has been studied for modeling complex dynamics. In this paper, we propose a Koopman modeling method based on an interpretable Koopman operator. The predominant merit of using the Koopman operator is to offer a linear infinite dimensional description of a nonlinear dynamical system with switching operators. In the proposed method, an enhanced learning-based extended dynamic mode decomposition (enhanced-EDMD) algorithm based on a novel eigenfunction construction method is proposed to obtain a finite-dimensional approximation of the Koopman operator. The convergence analysis of the enhanced-EDMD algorithm is also studied. Furthermore, to maximize the productivity of 1,3-PD and minimize the total variation in the optimal control within a time frame, an algorithm combining the model predictive control method with the enhanced learning-based EDMD (denoted by MPC-Enhanced-EDMD), based on gradient-based optimization and exact penalty function method, is proposed for devising optimal feeding rate of glycerol evolving with time. Numerical simulations are conducted by demonstrating the effectiveness of the enhanced-EDMD algorithm on the dynamics prediction and the MPC-Enhanced-EDMD method on the optimal feeding rates of glycerol.

Techno-commercial viability of glycerol valorization to 1,2- and 1,3-propanediol using pinch technology

Glycerol is a low-value by-product in biodiesel industries and an important platform chemical in biorefinery with vast derivative potentials. 1,2- and 1,3-Propanediol (PDO) are vital polymer precursors. Valorizing glycerol to PDOs is thus a promising approach for producing renewable chemicals and improving the economics of biodiesel industries. Therefore, this work demonstrated the techno-economic feasibility of PDOs for 100–2000 metric tons per day glycerol feed rate. 1,2-PDO was produced by selective hydrogenolysis of glycerol, while microbial batch and fed-batch fermentation of glycerol was considered for manufacturing 1,3-PDO with the co-production of 2,3-butanediol and ethanol. Pinch analysis was applied for process integration that reduced utility demands by around 19% for 1,2-PDO and 12–16% for 1,3-PDO. However, utilities were still major operating costs in these processes. Besides, utility consumptions and capital expenditures were considerably higher for 1,3-PDO by batch fermentation than 1,2-PDO due to low glycerol concentration (50 g/L). 1,3-PDO production cost (USD 3.42/kg) by batch fermentation was thus much more than 1,2-PDO (USD 0.98/kg). The minimum unitary selling price was USD 1.15 for 1,2-PDO and USD 4.90 for 1,3-PDO (batch) for 8.5% rate of return and five years payback period. However, the microbial 1,3-PDO produced by fed-batch fermentation was economically viable, with USD 0.78 and USD 1.02 as unitary production costs and minimum selling price.

Optimal switching control of 1,3-propanediol fed-batch production with a cost on smooth feeding rate variation

In this paper, we propose a nonlinear switched control system for microbial 1,3-propanediol (1,3-PD) fed-batch production, where the smooth feeding rate of glycerol as well as the switching instants between batch process and feeding process are taken as control variables. To maximize 1,3-PD yield and minimize the fluctuation of feeding rate, we then present an optimal switching control problem with a cost on the smooth feeding rate variation and subject to path constraints reflecting the operational requirements. For solving this problem, we convert it to a series of parameter optimization problems by using a novel control parameterization scheme, a time-scaling transformation and a constraint transcription technique. An analytical expression of the total variation for the smooth feeding rate is also derived. On this basis, we develop a parallel Particle Swarm Optimization (PSO) algorithm together with the gradient-based optimization to solve the resulting problem. Finally, numerical simulations indicate that sacrificing a small amount of 1,3-PD can reduce the feeding rate variation significantly.

Determination of feeding rate ratio in coupled fed-batch fermentation with pH feedback considering limited number of switches

This paper focuses on binary optimal control of fed-batch fermentation of glycerol by Klebsiella pneumoniaewith pH feedback considering limited number of switches. To maximize the concentration of 1,3-propanediol at terminal time, we propose a binary optimal control problem subjected to time-coupled combinatorial constraint with the ratio of feeding rate of glycerol to that of NaOH as control variables. Based on time-scaling transformation and discretization, the binary optimal control problem is first transformed into a mixed binary parameter optimization problem consisting of not only continuous variables but also binary variables, which is then divided into two subproblems via combinatorial integral approximation decomposition. Finally, a novel fruit fly optimizer with modified sine cosine algorithm and adaptive maximum dwell rounding are applied to solve the obtained subproblems numerically. Numerical results show the rationality and feasibility of the proposed method.

Environmental conditions during glycerol bioconversion affect 3-hydroxypropionic acid bioproduction by Limosilactobacillus reuteri DSM 17938.

3-Hydroxypropionic acid (3-HP) is a platform molecule whose biological production was carried out by the bacterium Limosilactobacillus reuteri according to a two-step process: first, a growth phase in batch mode on glucose, then a glycerol bioconversion into 3-HP in fed-batch mode. With the objective of improving 3-HP bioproduction, this study aimed at defining the operating conditions during the bioconversion phase that increases the bioproduction performance. A central composite rotatable design allowed testing various pH levels and specific glycerol feeding rates. By establishing response surfaces, optimal conditions have been identified that were different depending on the considered output variable (final 3-HP quantity, 3-HP production yield and production rate). Of them, 3-HP final quantity and 3-HP production yield were maximized at pH6.0 and at specific glycerol feeding rates of 60 and 55 mggly gCDW -1 h-1 , respectively. The specific 3-HP production rate was the highest at the upper limit of the specific substrate feeding rate (80 mggly gCDW -1 h-1 ) but was not affected by the pH. An additional experiment was carried out at pH6.0 and a specific glycerol feeding rate of 80 mggly gCDW -1 h-1 to validate the previous observations. In conclusion, the results showed a significant improvement of 3-HP concentration by 13%, of specific production rate by 34% and of 3-HP volumetric productivity by 39%, as compared to the initial values.

Generic model based control of different specific rates in recombinant E. coli Fed-batch processes

In addition to often reported control of the specific growth rate we show in this contribution a novel method to control the biomass specific substrate uptake as well as the protein production rate during the production phase of microbial fed-batch cultures. The control laws base on a calibrated process model including experimental data sets with different constant glycerol feed rates. The model includes changing growth and production behaviour in function of the induced metabolic stress. Based on the method of non-linear feedback linearization, the control laws were derived from the model, using the glycerol feed rate as the manipulable variable. Considering comparable setpoints at three different levels the effectiveness of the controller as well as their potential to improve the production phase was assessed by simulations. The direct control of product formation rates enables to ensure constant production performance and therefore to reach highest product levels in short time. As a drawback, the controller needs high feed adaption towards the end to counteract the advancing decay of the attainable production rates. This, to a lesser extend, also applies for the growth rate. A constant substrate uptake rate resulted in a valuable alternative to a uncontrolled, constant feed rate during the production phase of recombinant protein production processes.

Culture conditions affect Lactobacillus reuteri DSM 17938 ability to perform glycerol bioconversion into 3-hydroxypropionic acid

The platform molecule 3-hydroxypropionic acid (3-HP) can be produced using Lactobacillus reuteri through a two-step bioprocess that involves a growth phase followed by a bioconversion phase. The bioproduction is performed by resting cells that convert glycerol into 3-HP and 1,3-propanediol in fed-batch mode. This work aimed at studying the effect of the growth conditions of L.reuteri DSM 17938 during the first step, on the glycerol bioconversion into 3-HP during the second step. A Plackett and Burman design was carried out to test, in controlled bioreactors, the effect of 11 growth conditions simultaneously, at fixed bioconversion conditions. The supplementation of the growth medium with vitamin B12 and cysteine displayed a negative effect on the 3-HP bioproduction. The addition of glucose, phytone peptone, Tween 80, 1,2-propanediol and betaine in the growth medium, together with a low temperature and an optimal pH of 6.0 during the growth phase increased the bioconversion duration from 56h to 89hat a glycerol feeding rate of 0.5g·h-1. A validating experiment displayed that the 3-HP titer, 3-HP production yield and 3-HP specific production rate were significantly improved by 25 %, 150 % and 61 %, respectively.

Multi-objective optimization of a nonlinear switched time-delay system in microbial fed-batch process

For an uncoupled microbial fed-batch fermentation process of glycerol bioconversion to 1,3-propanediol (1,3-PD), we establish a nonlinear switched system model with free terminal time and unknown time-delays, in which the reaction mechanism of extracellular and intracellular environment and the regulation of dha regulator are considered. In order to evaluate the time-delays, a robustness index is given by a weighted sum of the expectation and variance of the relative deviation between system outputs before and after time-delays are perturbed. A multi-objective optimization model is proposed for the sake of maximization of 1,3-PD and minimization of consumption of glycerol coupling with minimization of the robustness index, where the continuous state inequality constraints are involved, and the time-delays, the feeding rates of glycerol and alkali, switching instants between batch and feeding modes, and terminal time of fermentation are regarded as the decision variables. For solving this multi-objective optimization problem, we convert it into a sequence of single-objective optimization problems by using the Normal Constraint method (NC). The gradient formulas involving multiple time-delays are discussed. An algorithm of Multi-objective Programming Approximation based on SQP (MPA-SQP) is described. By large calculations, a set of Pareto solutions are obtained, which provides some references for practical fermentation experiments.

Optimal minimal variation control with quality constraint for fed-batch fermentation processes involving multiple feeds

In this paper, an optimal minimal variation control in the fed-batch fermentation of glycerol bioconversion to 1,3-propanediol (1,3-PD) caused by Klebsiella pneumonia (K. pneumonia) is considered. In fed-batch process, it is required for the concentration of 1,3-PD to satisfy a quality constraint (i.e., the concentration of 1,3-PD at the terminal time is to reach a critical value), and furthermore, the cost associated with the change of the control signal must also be taken into account. It is formulated as an optimal control problem in which the total variation of the control signal is taken as the cost function, while the feeding rates of glycerol and alkali and the switching instants are taken as decision variables. The optimal control problem is subject to the quality constraint and certain continuous state inequality constraints. To handle the continuous state inequality constraints, the optimal control problem is approximated as a sequence of nonlinear programming subproblems. Because of the nature of the optimal control problem, which is highly complicated, a parallel algorithm is proposed to solve these subproblems based on genetic algorithm and the gradients of the constraint functions with respect to decision variables. From extensive simulation studies, it is observed that the obtained optimal feeding rates and switching instants are highly satisfactory.

Time-delay optimal control of a fed-batch production involving multiple feeds

In this paper, we consider time-delay optimal control of 1, 3-propan-ediol (1, 3-PD) fed-batch production involving multiple feeds. First, we propose a nonlinear time-delay system involving feeds of glycerol and alkali to formulate the production process. Then, taking the feeding rates of glycerol and alkali as well as the terminal time of process as the controls, we present a time-delay optimal control model subject to control and state constraints to maximize 1, 3-PD productivity. By a time-scaling transformation, we convert the optimal control problem into an equivalent problem with fixed terminal time. Furthermore, by applying control parameterization and constraint transcription techniques, we approximate the equivalent problem by a sequence of finite-dimensional optimization problems. An improved particle swarm optimization algorithm is developed to solve the resulting optimization problems. Finally, numerical results show that 1, 3-PD productivity increases considerably using the obtained optimal control strategy.

Dynamic optimization for the enzymatic production of acylglycerols

Optimal control of substrate feed rate in glycerolysis of vegetable oils was studied as a tool to improve monoacylglycerols (MAG) and diacylglycerols (DAG) production. Stochastic optimization strategy (Differential Evolutionary algorithm) was used to deal with the high complexity of the enzyme-catalyzed reactions dynamic behavior. Depending on the reaction system, optimal control of glycerol feed rate into the reaction showed to avoid enzymatic inhibition by the glycerol and improve acylglycerols yields up to 50% when compared to batch system. The obtained results showed that optimal control strategy can be used as an efficient tool to maximize the amount of desired product obtained by enzyme-catalyzed glycerolysis, particularly when the biocatalyst activity is significantly affected by substrate concentration.

Comparative Study of Fluid Package on Extractive Distillation of Ethanol-water Mixture Using Pure Glycerol and Ethylene Glycol as Extracting Solvents

The comparative study of Peng Robinson Strygek Vera (PRSV) and Non-Random Two Liquid (NRTL) fluid packages on the extractive distillation of ethanol-water mixture was done using pure glycerol and ethylene glycol as extracting agents. The process was simulated using HYSYS V. 8.4. Pure glycerol and ethylene glycol-glycerol mixture were used as separating agents. The results showed the highest molar composition of ethanol in the distillate at the solvent feed rate of 80 kmol/hr when pure glycerol was used with NRTL fluid package. With the PRSV fluid package the highest ethanol in the distillate was obtained at pure glycerol feed rate of 50 kmol/hr. The ethanol fraction in the distillate was decreasing with increasing ethylene glycol and decreasing glycerol in the ethylene glycol-glycerol mixture. The comparative study of the base case and alternative designs showed high ethanol composition in distillate in the range of 99.46 - 99.96% and 99.96 - 99.67% for NRTL and PRSV fluid package, respectively. It was concluded from the study that the PRSV fluid package could save cost of operation because of lower solvent requirement and energy consumption in the reboiler for both the base case and alternative designs.

Optimal control of nonlinear switched system in an uncoupled microbial fed-batch fermentation process

The bio-dissimilation of glycerol to 1,3-propanediol (1,3-PD) is a complex bioprocess due to the multiple inhibitions of substrate and products onto the cell growth. In consideration of both the inhibition mechanisms of 3-hydroxypropionaldehyde (3-HPA) and the transport modes of glycerol and 1,3-PD across the cell membrane, we establish a novel switched system which is represented by a ten-dimensional nonlinear dynamical equation containing both extracellular and intracellular environments. The uncoupled microbial fed-batch fermentation process are modeled using the switched system which the glycerol and alkali are respectively poured into. Taking the feeding rates of glycerol and alkali, the switching times and the mode sequence as the control variables, an optimal control model is proposed with the concentration of the terminal time 1,3-PD as performance index. In order to maximize the yield of 1,3-PD, the control parameterization technique and the exact penalty function method are used to solve the considered problem. Numerical results show that under the obtained optimal feeding rates of glycerol and alkali, switching times and mode sequence, the productivity of 1,3-PD at the terminal time is increased significantly compared with previous results.

Catalytic pyrolysis of crude glycerol over shaped ZSM-5/bentonite catalysts for bio-BTX synthesis

Ex-situ catalytic pyrolysis of crude glycerol for the synthesis of bio-based benzene, toluene and xylenes (bio-BTX) was performed in a tandem micro-reactor (TMR), a batch gram scale reactor and a continuous integrated bench scale unit using ZSM-5/bentonite extrudates. A bio-BTX yield of 8.1 wt.% (14.6% carbon yield) based on crude glycerol was obtained over the fresh catalysts (Cat-F) in the bench scale unit (crude glycerol feed rate of 200 g h−1, pyrolysis temperature of 520 °C and catalytic upgrading temperature of 536 °C). Catalyst activity was shown to be a function of the time on stream (TOS) and after 4.7 h the activity dropped with about 8%. After an oxidative regeneration step to remove coke, the activity of the regenerated catalysts (Cat-R1) was recovered to 95% of the original catalyst activity. After 11 reaction-regeneration cycles, the bio-BTX yield decreased to 5.4 wt.% (9.7% carbon yield) over Cat-R11. The fresh, deactivated and regenerated ZSM-5/bentonite catalysts were characterized in detail using nitrogen physisorption, XRD, ICP-AES, EA, TEM-EDX, TGA, NH3-TPD, pyridine-IR and solid MAS NMR. Coke (10.5 wt.% over Cat-D) was mostly deposited on ZSM-5 planes, and not only decreased the number of Lewis and Brönsted acid sites, but also blocked the pores, resulting in catalyst deactivation. Coke removal was effectively performed using an oxidative treatment. However, exchange of cations (e.g., Na) of the bentonite and possibly also from the crude glycerol feed with protons of ZSM-5 was observed, leading to irreversible deactivation. Furthermore, the layered structure of bentonite collapsed due to the removal of interlamellar water and dehydroxylation.

Robust multi-objective optimal switching control arising in 1,3-propanediol microbial fed-batch process

This paper considers optimal control of glycerol producing 1,3-propanediol (1,3-PD) via microbial fed-batch fermentation. The fed-batch process is formulated as a nonlinear switched time-delay system. In general, the time-delay in the fed-batch process cannot be exactly estimated. Our goal is to design an optimal switching control scheme to simultaneously maximize 1,3-PD productivity and 1,3-PD yield under time-delay uncertainty. Accordingly, we propose a robust multi-objective optimal switching control model, in which two objectives, i.e., 1,3-PD productivity and 1,3-PD yield, and their sensitivities with respect to uncertain time-delay are considered in the objective vector. The control variables in this problem are the feeding rate of glycerol, the switching instants and the terminal time of the process. By introducing an auxiliary dynamic system to calculate the objective sensitivities and performing a time-scaling transformation, we obtain an equivalent multi-objective optimal switching control problem in standard form. We then convert the equivalent multi-objective optimal control problem into a sequence of single-objective optimal switching control problems by using a modified normal boundary intersection method. A novel gradient-based single-objective solver combining control parameterization with constraint transcription technique is developed to solve these resulting single-objective optimal control problems. Finally, numerical results are provided to verify the effectiveness of the proposed solution approach.

Conversion of glycerol into syngas by rotating DC arc plasma

One of the most stable byproducts of biodiesel industry is glycerol, for which there’s lack of a large-scale application currently. Thermal plasma treatment is a potentially viable means of recycling glycerol by converting it into syngas. In this work, a rotating DC arc plasma reactor was used to decompose glycerol in order to produce syngas. The effect of plasma input power, glycerol feed rate, and water content in feedstock on the syngas conversion was investigated. It was found that the product gas stream, on an argon-free basis, contained 38% CO and 56% H2, with the balance being methane, ethylene, and little C4 hydrocarbons. Complete carbon conversion and energy conversion efficiency of 66% could be obtained with sufficient input power. Water content of feedstock influenced the amount of CO and H2 in the product gas. Magnetic flux intensity of the reactor showed negligible effect on the composition of the product gas, carbon conversion and energy conversion efficiency, but could prevent the anode and plasma reactor from severe erosion.

Comparison of constitutive and inducible β-fructofuranosidase production by recombinant Pichia pastoris in fed-batch culture using defined and semi-defined media

Short-chain fructooligosaccharides produced from sucrose by transfructosylation using β-fructofuranosidase (FFase), an industrially important enzyme, finds application in pre-biotics, sweeteners and confectionary products. Using recombinant Pichia pastoris, the influence of replacing the commonly-used Invitrogen® medium with a semi-defined medium for FFase production under the control of the glyceraldehyde-3-phosphate dehydrogenase (GAP) and alcohol oxidase (AOX) promoters was investigated. Replacing the trace metals (PTM1) solution with yeast extract resulted in a 54.3% decrease in FFase volumetric activity under control of the AOX promoter, suggesting a distinct requirement for trace metals for recombinant protein synthesis during methanol induction, given that the biomass yield on methanol decreased by only 10%. The same medium adjustment had no effect on enzyme production under GAP promoter control, although AOX promoter control resulted in double the FFase volumetric activity compared to glycerol-fed cultures. Decreasing basal salts by half did not affect the cultures, but alleviated precipitation during sterilisation. Optimisation of the glycerol feed rate and dissolved oxygen tension in DO-stat fed-batch fermentations using the semi-defined medium resulted in 17% increase in volutmetric activity of FFase expressed under the GAP promoter. This study highlighted the influence of carbon source and trace metals on heterologous protein production by P. pastoris using constitutive and inducible promoters.

Enhanced truncated-t-PA (CT-b) expression in high-cell-density fed-batch cultures of Pichia pastoris through optimization of a mixed feeding strategy by response surface methodology.

Recently, Pichia pastoris has been the focal point of interest as an expression system for production of many recombinant proteins. The study and optimization of feeding strategy are of major importance to achieve maximum volumetric productivity in fed-batch cultivations. Among different feeding strategies used in P. pastoris fed-batch cultures, those trying to maintain a constant specific growth rate have usually resulted in superior productivities. The objective of the present study was to investigate and optimize the co-feeding of glycerol and methanol to attain maximum expression of t-PA in P. pastoris fed-batch cultures with constant specific growth rate. The experiments were designed by response surface methodology, considering the specific feeding rates of methanol and glycerol as independent variables. In each experiment, glycerol and methanol were fed according to a predetermined equation to maintain a constant specific growth rate. It was found that with glycerol feeding for higher specific growth rates, the inhibitory properties of glycerol are more pronounced, while the best expression level was achieved when the ratio of µ set glycerol to that of methanol was around 1.67. In all specific growth rates tested, almost a similar ratio of the specific glycerol feeding rate to that of methanol led to the maximum protein production and activity. The statistical model predicted the optimal operating conditions for µ set glycerol and that of methanol to be 0.05 and 0.03 h(-1), respectively. Applying the optimum strategy, maximum of 52 g/L biomass, 300 mg/L t-PA and 340,000 IU/mL enzyme activity were obtained.

Bio-based 3-hydroxypropionic- and acrylic acid production from biodiesel glycerol via integrated microbial and chemical catalysis

Background3-Hydroxypropionic acid (3HP) and acrylic acid (AA) are industrially important platform- and secondary chemical, respectively. Their production from renewable resources by environment-friendly processes is desirable. In the present study, both chemicals were almost quantitatively produced from biodiesel-derived glycerol by an integrated process involving microbial and chemical catalysis.ResultsGlycerol was initially converted in a fed-batch mode of operation to equimolar quantities of 3HP and 1,3-propanediol (1,3PDO) under anaerobic conditions using resting cells of Lactobacillus reuteri as a biocatalyst. The feeding rate of glycerol was controlled at 62.5 mg/gCDW.h which is half the maximum metabolic flux of glycerol to 3HP and 1,3PDO through the L. reuteri propanediol-utilization (pdu) pathway to prevent accumulation of the inhibitory intermediate, 3-hydroxypronionaldehyde (3HPA). Subsequently, the cell-free supernatant containing the mixture of 3HP and 1,3PDO was subjected to selective oxidation under aerobic conditions using resting cells of Gluconobacter oxydans where 1,3PDO was quantitatively converted to 3HP in a batch system. The optimum conditions for the bioconversion were 10 g/L substrate and 5.2 g/L cell dry weight. Higher substrate concentrations led to enzyme inhibition and incomplete conversion. The resulting solution of 3HP was dehydrated to AA over titanium dioxide (TiO2) at 230 °C with a yield of >95 %.ConclusionsThe present study represents the first report on an integrated process for production of acrylic acid at high purity and -yield from glycerol through 3HP as intermediate without any purification step. The proposed process could have potential for industrial production of 3HP and AA after further optimization.Graphical abstractIntegrated three-step process for conversion of biodiesel glycerol to 3-hydroxypropionic acid (3HP) and acrylic acid (AA). Glycerol was initially converted to equimolar quantities of 3HP and 1,3-propanediol (1,3PDO) using resting cells of Lactobacillus reuteri. Subsequently, the cell-free supernatant containing the mixture of 3HP and 1,3PDO was subjected to selective oxidation using resting cells of Gluconobacter oxydans where 1,3PDO was quantitatively converted to 3HP. The resulting solution of 3HP was dehydrated to AA over titanium dioxide (TiO2) at 230 °C.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-015-0388-0) contains supplementary material, which is available to authorized users.

Biodiesel Residual Glycerol Metabolism by Klebsiella pneumoniae: Pool of Metabolites Under Anaerobiosis and Oxygen Limitation as a Function of Feeding Rates

The metabolism of residual glycerol from biodiesel synthesis by Klebsiella pneumoniae BLh-1 was investigated in this study. Batch and fed-batch cultivations were performed in bioreactors under anaerobic and oxygen limitation conditions. Results of batch cultivations showed that the main product was 1,3-propanediol (1,3-PD) in both conditions, although the higher yields and productivities (0.46mol mol(-1) glycerol and 1.22g L(-1) h(-1), respectively) were obtained under anaerobic condition. Large amounts of ethanol were also produced under batch anaerobic condition, peaking at 12.30g L(-1). Batch cultivations under oxygen limitation were characterized by faster growth kinetics, with higher biomass production but lower conversions of glycerol into 1,3-PD, with yields and productivities of 0.33mol mol(-1) glycerol and 0.99g L(-1) h(-1), respectively. The fed-batch cultivations were carried out in order to investigate the effects of feeding of raw glycerol on cells. Fed-batch under anaerobiosis showed that 1,3-PD and ethanol concentrations increased with the feeding rate, with maximal productions of 26.12 and 19.2g L(-1), respectively. The oxygen limitation conditions diverted the bacterium metabolism to an elevated lactic acid formation, reaching 59g L(-1) in higher feeding rates of glycerol, but lowering the production of ethanol.