Industrial-scale Fermentation Research Articles

Real-time and on-line monitoring of ethanol fermentation process by viable cell sensor and electronic nose

In this study, introduction of a viable cell sensor and electronic nose into ethanol fermentation was investigated, which could be used in real-time and on-line monitoring of the amount of living cells and product content, respectively. Compared to the conventional off-line biomass determination, the capacitance value exhibited a completely consistent trend with colony forming units, indicating that the capacitance value could reflect the living cells in the fermentation broth. On the other hand, in comparison to the results of off-line determination by high-performance liquid chromatography, the ethanol concentration measured by electronic nose presented an excellent consistency, so as to realize the on-line monitoring during the whole process. On this basis, a dynamic feeding strategy of glucose guided by the changes of living cells and ethanol content was developed. And consequently, the ethanol concentration, productivity and yield were enhanced by 15.4%, 15.9% and 9.0%, respectively. The advanced sensors adopted herein to monitor the key parameters of ethanol fermentation process could be readily extended to an industrial scale and other similar fermentation processes.

CRISPR/Cas-based genome editing in Aspergillus niger

Aspergillus niger is a vital industrial workhouse widely used for the production of organic acids and industrial enzymes. This fungus is a crucial cell factory due to its innate tolerance to a diverse range of abiotic conditions, high production titres, robust growth during industrial scale fermentation, and status as a generally recognized as safe (GRAS) organism. Rapid development of synthetic biology and systems biology not only offer powerful approaches to unveil the molecular mechanisms of A. niger productivity, but also provide more new strategies to construct and optimize the A. niger cell factory. As a new generation of genome editing technology, the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR associated (Cas) system brings a revolutionary breakthrough in targeted genome modification for A. niger. In this review, we focus on current advances to the CRISPR/Cas genome editing toolbox, its application on gene modification and gene expression regulation in this fungal. Moreover, the future directions of CRISPR/Cas genome editing in A. niger are highlighted.

Dynamics of changes in organic acids, sugars and phenolic compounds and antioxidant activity of sea buckthorn and sea buckthorn-apple juices during malolactic fermentation.

Sea buckthorn (Hippophaë rhamnoides L.) berries have high biological value as a rich source of phenolic compounds, fatty acids and vitamins A, C, E. Due to the high organic acid content and sour taste, the fruits are rarely used in juice production. Therefore, the study aimed to determine the metabolic activity of Lactobacillus plantarum, Lactobacillus plantarum subsp. argentoratensis and Oenococcus oeni strains along with the dynamics of changes in organic acids, sugars, phenolic compounds, and antioxidant activity during 72-h fermentation of 100% sea buckthorn and mixed with apple (1:1) juices. The strongest malolactic conversion was in mixed juices (to 75.0%). The most efficient strains were L. plantarum DSM 10492, 20174 and 6872. L. plantarum strains caused an increase in flavonols and antioxidant activity of sea buckthorn-apple juices. The results can be used to select conditions and strains in industrial-scale fermentation, to produce novel sea buckthorn products and increase their consumption.

The feather degradation mechanisms of a new Streptomyces sp. isolate SCUT-3

Feather waste is the highest protein-containing resource in nature and is poorly reused. Bioconversion is widely accepted as a low-cost and environmentally benign process, but limited by the availability of safe and highly efficient feather degrading bacteria (FDB) for its industrial-scale fermentation. Excessive focuses on keratinase and limited knowledge of other factors have hindered complete understanding of the mechanisms employed by FDB to utilize feathers and feather cycling in the biosphere. Streptomyces sp. SCUT-3 can efficiently degrade feather to products with high amino acid content, useful as a nutrition source for animals, plants and microorganisms. Using multiple omics and other techniques, we reveal how SCUT-3 turns on its feather utilization machinery, including its colonization, reducing agent and protease secretion, peptide/amino acid importation and metabolism, oxygen consumption and iron uptake, spore formation and resuscitation, and so on. This study would shed light on the feather utilization mechanisms of FDBs.

Harnessing the intracellular triacylglycerols for titer improvement of polyketides in Streptomyces.

Pharmaceutically important polyketides such as avermectin are mainly produced as secondary metabolites during the stationary phase of growth of Streptomyces species in fermenters. The source of intracellular metabolites that are funneled into polyketide biosynthesis has proven elusive. We applied multi-omics to reveal that intracellular triacylglycerols (TAGs), which accumulates in primary metabolism, are degraded during stationary phase. This process could channel carbon flux from both intracellular TAGs and extracellular substrates into polyketide biosynthesis. We devised a strategy named 'dynamic degradation of TAG' (ddTAG) to mobilize the TAG pool and increase polyketide biosynthesis. Using ddTAG we increased the titers of actinorhodin, jadomycin B, oxytetracycline and avermectin B1a in Streptomyces coelicolor, Streptomyces venezuelae, Streptomyces rimosus and Streptomyces avermitilis. Application of ddTAG increased the titer of avermectin B1a by 50% to 9.31 g l-1 in a 180-m3 industrial-scale fermentation, which is the highest titer ever reported. Our strategy could improve polyketide titers for pharmaceutical production.

Sparse PARAFAC2 decomposition: Application to fault detection and diagnosis in batch processes

The PARAFAC2 decomposition is often used to modeling a set of matrices that have the same number of columns but different numbers of rows. However, the PARAFAC2 model lacks of interpretability because most of elements in factor vectors are nonzero. To overcome this deficiency, a sparse PARAFAC2 (SPARAFAC2) decomposition is developed. SPARAFAC2 yields sparse factor vectors (SFVs) with only a few nonzero elements. Because of the sparsity in factor vectors, the SPARAFAC2 model has much better interpretability than the ordinary PARAFAC2 model. SPARAFAC2 is attractive for the applications in batch processes, because it not only can directly handle the three-way structure of batch data and naturally solve the unequal batch length problem, but also can reveal meaningful connections between process variables. Therefore, based on the SPARAFAC2 decomposition, fault detection and diagnosis methods are proposed for batch processes. To improve the fault detection capability, a cumulative percent contribution criterion is used to adaptively select SFVs for each sample from the fault detection point of view. Two fault detection indices are then defined using the selected SFVs. A contribution-based fault diagnosis method is also proposed. This method identifies faulty variables by evaluating contributions of SFVs and active variables (with nonzero elements) in each SFV to the detection of faults. The effectiveness of the proposed methods is demonstrated with a case study in an industrial-scale fermentation process.

Controlled Reduction of Genomic Heterozygosity in an Industrial Yeast Strain Reveals Wide Cryptic Phenotypic Variation.

Abundant genomic heterozygosity can be found in wild strains of the budding yeast Saccharomyces cerevisiae isolated from industrial and clinical environments. The extent to which heterozygosity influences the phenotypes of these isolates is not fully understood. One such case is the PE-2/JAY270 strain, a natural hybrid widely adopted by sugarcane bioethanol distilleries for its ability to thrive under harsh biotic and abiotic stresses during industrial scale fermentation, however, it is not known whether or how the heterozygous configuration of the JAY270 genome contributes to its many desirable traits. In this study, we took a step toward exploring this question by conducting an initial functional characterization of JAY270’s heteroalleles. We manipulated the abundance and distribution of heterozygous alleles through inbreeding and targeted uniparental disomy (UPD). Unique combinations of homozygous alleles in each inbred strain revealed wide phenotypic variation for at least two important industrial traits: Heat stress tolerance and competitive growth. Quantitative trait loci analyses allowed the identification of broad genomic regions where genetic polymorphisms potentially impacted these traits, and there was no overlap between the loci associated with each. In addition, we adapted an approach to induce bidirectional UPD of three targeted pairs of chromosomes (IV, XIV, and XV), while heterozygosity was maintained elsewhere in the genome. In most cases UPD led to detectable phenotypic alterations, often in opposite directions between the two homozygous haplotypes in each UPD pair. Our results showed that both widespread and regional homozygosity could uncover cryptic phenotypic variation supported by the heteroalleles residing in the JAY270 genome. Interestingly, we characterized multiple examples of inbred and UPD strains that displayed heat tolerance or competitive growth phenotypes that were superior to their heterozygous parent. However, we propose that homozygosity for those regions may be associated with a decrease in overall fitness in the complex and dynamic distillery environment, and that may have contributed to slowing down the erosion of heterozygosity from the JAY270 genome. This study also laid a foundation for approaches that can be expanded to the identification of specific alleles of interest for industrial applications in this and other hybrid yeast strains.

Accurate and cost-effective prediction of HBsAg titer in industrial scale fermentation process of recombinant Pichia pastoris by using neural network based soft sensor.

In the current work, the attempt was made to apply best-fitted artificial neural network (ANN) architecture and the respective training process for predicting final titer of hepatitis B surface antigen (HBsAg), produced intracellularly by recombinant Pichia pastoris Mut+ in the commercial scale. For this purpose, in large-scale fed-batch fermentation, using methanol for HBsAg induction and cell growth, three parameters of average specific growth rate, biomass yield, and dry biomass concentration-in the definite integral form with respect to fermentation time-were selected as input vectors; the final concentration of HBsAg was selected for the ANN output. Used dataset consists of 38 runs from previous batches; feed-forward ANN 3:5:1 with training algorithm of backpropagation based on a Bayesian regularization was trained and tested with a high degree of accuracy. Implementing the verified ANN for predicting the HBsAg titer of the five new fermentation runs, excluded from the dataset, in the full-scale production, the coefficient of regression and root-mean-square error were found to be 0.969299 and 2.716774, respectively. These results suggest that this verified soft sensor could be an excellent alternative for the current relatively expensive and time-intensive analytical techniques such as enzyme-linked immunosorbent assay in the biopharmaceutical industry.

Antagonistic lactic acid bacteria in association with Saccharomyces cerevisiae as starter cultures for standardization of sour cassava starch production

In order to improve cassava's palatability and reduce its toxicity, this root is fermented and applied in foods, such as sour cassava starch used to prepare cheese bread and biscuits. This fermentation occurs spontaneously with lactic acid bacteria (LAB) and yeasts. However, it remains an empirical process, with long duration and lack of product quality homogeneity. This work aims to use starter cultures in a pilot-scale fermentation process for the production of sour cassava starch. After differentiation of strains, Lactobacillus plantarum Lp3, which exhibited great total titratable acidity (TTA) (5.01 ± 0.05%) and antagonistic activity against Bacillus cereus, Escherichia coli and Salmonella Typhimurium, together with Lactobacillus brevis Lb9 (with lesser TTA values: 2.71 ± 0.10%, but amylolytic activity: 2.75 ± 0.61mm) were tested as single and co-cultures with Saccharomyces cerevisiae UFMG-A1007. LAB and yeasts were inoculated at counts of 8 and 7 log10 CFU/g, respectively, and they remained until the 28th day only in co-culture, highlighting the importance of the yeast for the LAB viability. Although single cultures lead to higher acidity during fermentation, the final product acidity obtained with single cultures did not differ from the acidity obtained with L. plantarum Lp3 in association with S. cerevisiae UFMG-A1007. Therefore, this co-culture exhibited higher potential to be tested as a starter culture in industrial-scale fermentation studies because both microorganisms were in high counts until the end of fermentation and contributed to a final product safe for human consumption, with satisfactory acidity, expansion capacity, and physicochemical properties.

Regulatory associations between the metabolism of sulfur-containing amino acids and xanthan biosynthesis in Xanthomonas campestris pv. campestris B100.

The γ-proteobacterium Xanthomonas campestris pv. campestris (Xcc) B100 synthesizes the exopolysaccharide xanthan, a commercially relevant thickening agent produced commonly by industrial scale fermentation. This work was inspired by the observation that methionine is an inhibitor of xanthan formation in growth experiments. Therefore, the global effects of methionine supplementation were characterized through cultivation experiments, genome-wide microarray hybridizations and qRT-PCR. Specific pull down of DNA-binding proteins by using the intergenic regions upstream of xanA, gumB and gumD led to the identification of six transcriptional regulators, among them the LysR-family transcriptional regulator CysB. An insertion mutant of this gene was analyzed by growth experiments, microarray experiments and qRT-PCR. Based on our experimental data, we developed a model that describes the methionine-dependent co-regulation of xanthan and sulfur-containing compounds in Xanthomonas. These data substantially contribute to better understand the impact of methionine as a compound in xanthan production media used in industrial fermentations.

Removal of Bacterial Contamination from Bioethanol Fermentation System Using Membrane Bioreactor

A major issue hindering efficient industrial ethanol fermentation from sugar-based feedstock is excessive unwanted bacterial contamination. In industrial scale fermentation, reaching complete sterility is costly, laborious, and difficult to sustain in long-term operation. A physical selective separation of a co-culture of Saccharomyces cerevisiae and an Enterobacter cloacae complex from a buffer solution and fermentation media at dilution rates of 0.1–1 1/h were examined using an immersed membrane bioreactor (iMBR). The effect of the presence of yeast, inoculum size, membrane pore size, and surface area, backwashing and dilution rate on bacteria removal were assessed by evaluating changes in the filtration conditions, medium turbidity, and concentration of compounds and cell biomass. The results showed that using the iMBR with dilution rate of 0.5 1/h results in successful removal of 93% of contaminating bacteria in the single culture and nearly complete bacteria decontamination in yeast-bacteria co-culture. During continuous fermentation, application of lower permeate fluxes provided a stable filtration of the mixed culture with enhanced bacteria washout. This physical selective separation of bacteria from yeast can enhance final ethanol quality and yields, process profitability, yeast metabolic activity, and decrease downstream processing costs.

Chemical profile and in-vitro pharmacological activities of yellow pigment extracted from Arthrobacter gandavensis

Abstract Natural pigments have captivated pharmaceutical, food, textile and cosmetic markets because of its low toxicity as compared to synthetic pigments. Microorganisms, especially bacteria are the diverse source of natural pigments. The present study is performed with the aim to investigate different biological activities in pigment extracts from bacteria. A strain producing yellow pigment was identified as Arthrobacter gandavensis (Accession # MH187869) by 16S ribosomal RNA gene sequencing. Pigment was extracted and analyzed for various activities such as antibacterial, anticancer, antileishmanial, hemolytic, protein kinase inhibition and antioxidative activities. Total phenolic and flavonoid contents were also determined. An antibacterial study showed that the yellow pigment was found to be active against Klebsiella pneumoniae, Enterobacter sakazakii and Salmonella typhi with 10 ± 0.43 mm, 9 ± 0.77 mm and 80.98 mm zone of inhibition, respectively. Significantly high activity was noted against HepG2 cell lines (67%) at concentrations of 250 μg/mL and leishmania cell culture (82%) at concentrations of 1000 μg/mL were also noted. Similarly, results obtained from the other aforementioned activities were found to be dose-dependent, as the activity of the sample was found to be increased with a progressive increase in sample concentration. Some compounds (-Carotenold P468, capsorubin and 2-Butene-1-ol-3-methyl-acetate) were identified through HPLC and GCMS analysis. Similarly, results of the current study show that the yellow pigment is active in diverse biological activities. In conclusion, the yellow pigments isolated from Arthrobacter gandavensis covers a broad range pharmacological activities, which is ideal for industrial scale fermentation.

Enhanced fermentative performance under stresses of multiple lignocellulose-derived inhibitors by overexpression of a typical 2-Cys peroxiredoxin from Kluyveromyces marxianus

BackgroundBioethanol from lignocellulosic materials is of great significance to the production of renewable fuels due to its wide sources. However, multiple inhibitors generated from pretreatments represent great challenges for its industrial-scale fermentation. Despite the complex toxicity mechanisms, lignocellulose-derived inhibitors have been reported to be related to the levels of intracellular reactive oxygen species (ROS), which makes oxidoreductase a potential target for the enhancement of the tolerance of yeasts to these inhibitors.ResultsA typical 2-Cys peroxiredoxin from Kluyveromyces marxianus Y179 (KmTPX1) was identified, and its overexpression was achieved in Saccharomyces cerevisiae 280. Strain TPX1 with overexpressed KmTPX1 gene showed an enhanced tolerance to oxidative stresses. Serial dilution assay indicated that KmTPX1 gene contributed to a better cellular growth behavior, when the cells were exposed to multiple lignocellulose-derived inhibitors, such as formic acid, acetic acid, furfural, ethanol, and salt. In particular, KmTPX1 expression also possessed enhanced tolerance to a mixture of formic acid, acetic acid, and furfural (FAF) with a shorter lag period. The maximum glucose consumption rate and ethanol generation rate in KmTPX1-expressing strain were significantly improved, compared with the control. The mechanism of improved tolerance to FAF depends on the lower level of intracellular ROS for cell survival under stress.ConclusionA new functional gene KmTPX1 from K. marxianus is firstly associated with the enhanced tolerance to multiple lignocellulose-derived inhibitors in S. cerevisiae. We provided a possible detoxification mechanism of the KmTPX1 for further theoretical research; meanwhile, we provided a powerful potential for application of the KmTPX1 overexpressing strain in ethanol production from lignocellulosic materials.

A set of isomeric episomal plasmids for systematic examination of mitotic stability in Saccharomyces cerevisiae.

Yeast episomal shuttle vectors (YEp type) are commonly used in fundamental research and biotechnology whenever elevated product levels are desired. Their instability, however, poses an impediment not only in industrial scale fermentation. In order to analyse instability which might be linked to plasmid structure, a series of YEp type plasmids that are identical in size has been assembled, differing only in the overall arrangement of the fragments used. The performance of the eight plasmid isoforms was studied with respect to mitotic stability. While transformation efficiency in two laboratory strains of Saccharomyces cerevisiae does not differ dramatically between the eight plasmids, the plasmids do not, however, perform equally well in terms of segregational stability. Although stable at about 90% plasmid‐bearing cells in selective medium, under non‐selective conditions, three plasmid forms performed better than the other five with an up to 5.7‐fold higher stability as compared with the least favourable isoform. In a subset of four plasmids (including stable and unstable isoforms) copy numbers were determined. Furthermore the functionality of the selection marker was characterized with respect to plasmid‐derived relative HIS3 transcript levels. No significant differences in HIS3 transcript levels could be observed between strains carrying any one of the four plasmids. Ruling out copy number and performance of HIS3, the results indicate nevertheless that plasmid architecture has an impact on mitotic segregation in yeast and that construction of an expression vector should take into account that the plasmid backbone itself might already show a more or less favourable arrangement of its segments. © 2017 The Authors. Yeast published by John Wiley & Sons, Ltd.

DSM, Evonik form omega-3 joint venture

DSM and Evonik Industries are setting up a joint venture to make omega-3 fatty acids from natural marine algae for use in fish feed and pet food. The venture, called Veramaris, will spend $200 million to build an omega-3 fatty acid facility at an existing Evonik site in the U.S. It will go onstream in 2019. The firms have already made pilot-scale quantities of the oil at DSM’s facility in Kingstree, S.C. The new plant will turn out a “highly concentrated algal oil,” the partners say, using algae production expertise from DSM and industrial-scale fermentation know-how from Evonik. Omega-3 fatty acids are a family of polyunsaturated fats that include eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Initial output from the planned facility will meet about 15% of the farmed salmon industry’s demand for EPA and DHA, the two firms say. Fish use omega-3 for metabolic functions and as a cellular

Metabolic engineering of Bacillus subtilis for chiral pure meso-2,3-butanediol production.

Background2,3-Butanediol (2,3-BD) with low toxicity to microbes, could be a promising alternative for biofuel production. However, most of the 2,3-BD producers are opportunistic pathogens that are not suitable for industrial-scale fermentation. In our previous study, wild-type Bacillus subtilis 168, as a class I microorganism, was first found to generate only d-(−)-2,3-BD (purity >99 %) under low oxygen conditions.ResultsIn this work, B. subtilis was engineered to produce chiral pure meso-2,3-BD. First, d-(−)-2,3-BD production was abolished by deleting d-(−)-2,3-BD dehydrogenase coding gene bdhA, and acoA gene was knocked out to prevent the degradation of acetoin (AC), the immediate precursor of 2,3-BD. Next, both pta and ldh gene were deleted to decrease the accumulation of the byproducts, acetate and l-lactate. We further introduced the meso-2,3-BD dehydrogenase coding gene budC from Klebsiellapneumoniae CICC10011, as well as overexpressed alsSD in the tetra-mutant (ΔacoAΔbdhAΔptaΔldh) to achieve the efficient production of chiral meso-2,3-BD. Finally, the pool of NADH availability was further increased to facilitate the conversion of meso-2,3-BD from AC by overexpressing udhA gene (coding a soluble transhydrogenase) and low dissolved oxygen control during the cultivation. Under microaerobic oxygen conditions, the best strain BSF9 produced 103.7 g/L meso-2,3-BD with a yield of 0.487 g/g glucose in the 5-L batch fermenter, and the titer of the main byproduct AC was no more than 1.1 g/L.ConclusionThis work offered a novel strategy for the production of chiral pure meso-2,3-BD in B. subtilis. To our knowledge, this is the first report indicating that metabolic engineered B. subtilis could produce chiral meso-2,3-BD with high purity under limited oxygen conditions. These results further demonstrated that B. subtilis as a class I microorganism is a competitive industrial-level meso-2,3-BD producer.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0502-5) contains supplementary material, which is available to authorized users.

Economic Evaluation of <i>Streptococcus Pneumoniae</i> Culture Media

Streptococcus pneumoniae, a major bacterial pathogen worldwide, requires a complex medium for culture, which complicates harvesting of antigens for vaccine production. Here we present an economic evaluation of factors affecting the production cost of a chemically defined medium for the scale up of fermentation of S. pneumoniae, compared with the most traditional fermentation media. A basic laboratory-scale experiment of 1 L and an industrial-scale production of 100 L were assumed. The economic analysis results show that at 1 L lab-scale the Chemically Defined Medium (CDM) is the most expensive (US$35/L) compared to Tryptic Soy Broth medium (TSB) and Tryptic Soy Vegitone medium (TSBv), (US$2.9/L), Todd Hewitt (US$22.8/L) and Brain Heart Broth (BHI) (US$10.8/L). However at 100 L production-scale all the media costs decrease and CDM becomes competitive with Todd Hewitt and BHI (US$8.4, 9.6, 8.2/L, respectively) and slightly more expensive than both TSB media (US$2.9/L). We conclude that although some aspects of culture growth should be studied in more detail, the production cost of the chemically defined medium for industrial scale fermentation of S. pneumoniae is economically competitive on the grounds not only of price, but also taking into account other benefits such us ease of isolation, and the possibility of fine-tuning of the individual chemical species in its formulation according to the culture requirements.

Recent Advances in Biobutanol Production

Abstract Butanol has been used as an important solvent in various industries, and is considered a good liquid fuel substitute for gasoline for use in internal combustion engines. Biobased production of butanol has a long history and was one of the first industrial-scale fermentation processes in which Clostridium strains were employed. Recent work on metabolic engineering of Clostridium strains has resulted in considerably improved production of butanol. In addition, several non-clostridial microorganisms have also been developed for butanol production. Here we review the advances in butanol production that have employed Clostridium strains and other microorganisms.

Industrial-scale culturing of the crude oil-degrading marine Acinetobacter sp. strain HC8-3S

The marine bacterium Acinetobacter sp. strain HC8-3S, capable of degrading petroleum hydrocarbons, was previously shown to be applicable for bioremediation. Here, we evaluated the performance of the strain during industrial-scale fermentation, long-term storage, and biodegradation processes. Fermentation parameters were optimized for industrial-scale culturing using lower salinity and fewer inorganic salts in the culture medium. The shelf-life of the fermentation broth was evaluated in different storage conditions. Biodegradation efficiency of the strain was evaluated using gas chromatography. Results indicated that the optimum conditions for one-ton scale fermentation were 30 °C, pH 7.4–7.8, and rotation speed 90 rpm; the cell density reached 3.6 ± 1.9 × 1010 CFU ml−1 after 12 h. The low temperature can preserved fermentation broth for longer time. When the storage temperature was down to 4 °C from room temperature, half-life of strain HC8-3S extended from 9 days to 34 days. The biodegradation rate of the saturated hydrocarbon fraction of crude oil was 94% after treatment with the strain for 5 days. The results indicate that Acinetobacter sp. strain HC8-3S can be enriched efficiently on a large scale, making it a potentially useful industrial strain. This crude oil degradative capability of the strain HC8-3S provides possible application for the clean-up of crude oil-contaminated environment.

Engineering Corynebacterium glutamicum for the production of 2,3-butanediol

Background2,3-Butanediol is an important bulk chemical with a wide range of applications. In bacteria, this metabolite is synthesised from pyruvate via a three-step pathway involving α-acetolactate synthase, α-acetolactate decarboxylase and 2,3-butanediol dehydrogenase. Thus far, the best producers of 2,3-butanediol are pathogenic strains, hence, the development of more suitable organisms for industrial scale fermentation is needed. Herein, 2,3-butanediol production was engineered in the Generally Regarded As Safe (GRAS) organism Corynebacterium glutamicum. A two-stage fermentation process was implemented: first, cells were grown aerobically on acetate; in the subsequent production stage cells were used to convert glucose into 2,3-butanediol under non-growing and oxygen-limiting conditions.ResultsA gene cluster, encoding the 2,3-butanediol biosynthetic pathway of Lactococcus lactis, was assembled and expressed in background strains, C. glutamicum ΔldhA, C. glutamicum ΔaceEΔpqoΔldhA and C. glutamicum ΔaceEΔpqoΔldhAΔmdh, tailored to minimize pyruvate-consuming reactions, i.e., to prevent carbon loss in lactic, acetic and succinic acids. Producer strains were characterized in terms of activity of the relevant enzymes in the 2,3-butanediol forming pathway, growth, and production of 2,3-butanediol under oxygen-limited conditions. Productivity was maximized by manipulating the aeration rate in the production phase. The final strain, C. glutamicum ΔaceEΔpqoΔldhAΔmdh(pEKEx2-als,aldB,PtufbutA), under optimized conditions produced 2,3-butanediol with a 0.66 mol mol−1 yield on glucose, an overall productivity of 0.2 g L−1 h−1 and a titer of 6.3 g L−1.ConclusionsWe have successfully developed C. glutamicum into an efficient cell factory for 2,3-butanediol production. The use of the engineered strains as a basis for production of acetoin, a widespread food flavour, is proposed.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-015-0362-x) contains supplementary material, which is available to authorized users.