Erythritol Yield Research Articles

Effect of low frequency alternating magnetic field for erythritol production in Yarrowia lipolytica.

Numerous works have reported that magnetic fields serve as signals capable of influencing microbial metabolism. However, little is known about the effect of magnetic field on erythritol production by the model microorganism Yarrowia lipolytica (Y. lipolytica). Therefore, we investigated the effect of low-frequency alternating magnetic fields (LF-AMF) with different magnetic field intensities (0-1.5mT) and different magnetic field treatment times (1-10 days) on the production of erythritol by Y. lipolytica -JZ204. The optimal treatment condition was 0.5mT for 8 days. As a result, a maximal erythritol yield was achieved 63.74g/L, the biomass was reached 37g/L, and the specific erythritol yield per unit of biomass was 1.7227g/g, which were 60.72%, 32.09%, and 24.85% higher than the control, respectively. We investigated the internal mechanism of magnetic fields impact by using transcriptomics and RT-qPCR technology. This study demonstrated the effectiveness of LF-AMF in enhancing erythritol production by Y. lipolytica JZ-204, providing insights for the application of magnetic field in assisting microbial fermentation and improving the synthesis of beneficial products.

Strain improvement for enhanced erythritol production by Moniliella pollinis Mutant-58 using jaggery as a cost-effective substrate.

Erythritol has been produced by various microorganisms including Yarrowia, Moniliella, Aureobasidium, and Candida strains. Due to its relatively high price, erythritol sweetener is used lesser than other polyols despite having many advantages. Therefore, in this study, Moniliella pollinis strain was improved for erythritol production by chemical mutagenesis and subsequently screening for cost-effective carbon sources for the enhanced erythritol yield. M. pollinis was subjected to N-methyl N-nitro N-nitroso guanidine (NTG), ethyl methyl sulfonate (EMS), and UV mutagenesis for improved erythritol production. The fmutant strains were evaluated for enhanced erythritol production medium optimization by using different carbon substrates at the shake flask level. To enhance the production of erythritol and statistical media, optimization was carried out using a central composite design (CCD). Among 198 isolated mutants, Mutant-58 strain generated by EMS mutagenesis was selected for further assessment. The Mutant-58 strain showed significant morphological changes as compared to the parent strain. Furthermore, statistically optimized media composition resulted in the higher production of erythritol (91.2 ± 3.4 g/L) with a yield of 40.7 ± 3.4 % in shake flask experiments. The optimized medium composition for erythritol production constitutes (g/L) 225 jaggery, 4.4 yeast extract (YE), 4.4 KH2PO4, 0.31 MgSO4, and pH 5.5. The present study demonstrated strain improvement, media, and process optimization resulting in a 30% increase in the erythritol production in the Mutant-58 as compared to the parent strain. This is also the first instance where jaggery has been used as a cost-effective carbon source alternative to glucose for industrial-scale erythritol production.

Establishment of picodroplet-based co-culture system to improve erythritol production in Yarrowia lipolytica

Fluorescence-activated droplet sorting (FADS) combined with transcription factor (TF)-based biosensors allows for the high-throughput isolation of clones that overproduce extracellular metabolites. Here, we developed a FADS-TF coculture pipeline for improving erythritol production in Yarrowia lipolytica. The pipeline comprises three droplet operation steps: the generation and incubation of droplets that encapsulate yeast mutants with single-cell resolution, the pico-injection of fluorescence-based erythritol-biosensing Escherichia coli, and the sorting of the highest fluorescence droplets with an approximately 1 ‰ survival ratio. With the picodroplet-based workflow, we initially carried out a two-stage temperature and pH control strategy on the droplets to separate the erythritol production and detection processes. We then eliminated the background expression of biosensors by utilizing pH-sensitive erythromycin, finally establishing a complete version of the coculture screening system. The optimal strain, Yarrowia lipolytica S4-9, contributed 231.2 g/L erythritol after a 114-h fermentation and was successfully screened from the fourth round of the mutant library. Compared to the parent, the erythritol yield and production rate of Yarrowia lipolytica S4-9 increased by 16.97 % and 26.09 %, respectively, in a 5-L bioreactor. Our results indicated that FADS-TFs have great potential for the high-throughput screening of extracellular products as additional biosensors become available.

Enhancing erythritol production from crude glycerol in a wild-type Yarrowia lipolytica by metabolic engineering.

Background: Erythritol is a zero-calorie sweetener that is widely used in the food, pharmaceutical, and medical industries. Crude glycerol is the main by-product of biodiesel, and the effective utilization of crude glycerol will help to improve biodiesel viability. Previous studies on the production of erythritol from Y. lipolytica using crude glycerol as a carbon source have focused on optimizing the fermentation process of the mutant Y. lipolytica Wratislavia K1, while metabolic engineering has not been successfully applied. Results: To this end, we engineered the yeast Y. lipolytica to increase the productivity of this strain. Wild strains tolerant to high concentrations of crude glycerol were screened and identified. A series of rational metabolic approaches were employed to improve erythritol production. Among them, the engineered strain Y-04, obtained by tandem overexpression of GUT1 and GUT2, significantly increased glycerol assimilation by 33.3%, which was consistent with the results of RT-qPCR analysis. The effects of tandem overexpression of GUT1, GUT2, TKL1, and TAL1 on erythritol synthesis were also evaluated. The best results were obtained using a mutant that overexpressed GUT1, GUT2, and TKL1 and knocked out EYD1. The final Y-11 strain produced 150 g/l erythritol in a 5-L bioreactor with a yield and productivity of 0.62 g/g and 1.25 g/l/h, respectively. To the best of our knowledge, this is the highest erythritol yield and productivity from crude glycerol ever reported in Y. lipolytica. Conclusion: This work demonstrated that overexpression of GUT1, GUT2, and TKL1 and knockdown of EYD1 could be used to improve crude glycerol utilization and erythritol synthesis in Y. lipolytica. The process parameters such as erythritol yield and productivity were significantly elevated, which is valuable for industrial applications. Crude glycerol, as a carbon source, could efficiently restrict the synthesis of by-products while enhancing the generation of erythritol, compared to glucose. This indicates considerable potential for synthesizing value-added products from crude glycerol by Y. lipolytica.

Fermentative Production of Erythritol from Cane Molasses Using Candida magnoliae: Media Optimization, Purification, and Characterization

Erythritol is a natural, zero-calorie sweetener that can be used as a sugar substitute and humectant for different products such as confectionaries, tablets, etc. Methods such as extraction and chemical synthesis for erythritol synthesis are not feasible or sustainable due to lower yield and higher operating costs. In the present study, erythritol is produced through the submerged fermentation of cane molasses, a by-product of the cane sugar industry, in the presence of the osmophilic yeast Candida magnoliae. Erythrose reductase enzyme assay was used for quantifying erythritol yield. Plackett–Burman’s design screened the three most influential factors viz. molasses, yeast extract, and KH2PO4 out of 12 contributing factors. Further, the concentration of molasses (200–300 g/L), yeast extract (9–12 g/L), and KH2PO4 (2–5 g/L) were optimized using response surface methodology coupled with numerical optimization. The optimized erythritol yield (99.54 g·L−1) was obtained when the media consisted of 273.96 g·L−1 molasses, 10.25 g·L−1 yeast extract, and 3.28 g·L−1 KH2PO4 in the medium. After purification, the liquid chromatography–mass spectrometry (LC-MS) analysis of erythritol crystals from this optimized fermentation condition showed 94% purity. Glycerol was produced as the side product (5.4%) followed by a trace amount of sucrose and mannitol. The molecular masses of the erythritol were determined through mass spectrometry by comparing [M + Na] + ions. Analysis in electrospray (ES) positive mode gave (m/z) of 145.12 [M + 23]. This study has reported a higher erythritol yield from molasses and used osmotolerant yeast Candida magnoliae to assimilate the sucrose from molasses.

The Overexpression of YALI0B07117g Results in Enhanced Erythritol Synthesis from Glycerol by the Yeast Yarrowia lipolytica.

The unconventional yeast Yarrowia lipolytica is used to produce erythritol from glycerol. In this study, the role of the erythrose reductase (ER) homolog YALI0B07117g in erythritol synthesis was analyzed. The deletion of the gene resulted in an increased production of mannitol (308%) and arabitol (204%) before the utilization of these polyols began. The strain overexpressing the YALI0B07117g gene was used to increase the erythritol yield from glycerol as a sole carbon source in batch cultures, resulting in a yield of 0.4 g/g. The specific consumption rate (qs) increased from 5.83 g/g/L for the WT strain to 8.49 g/g/L for the modified strain and the productivity of erythritol increased from 0.28 g/(L h) for the A101 strain to 0.41 g/(L h) for the modified strain. The application of the research may prove positive for shortening the cultivation time due to the increased rate of consumption of the substrate combined with the increased parameters of erythritol synthesis.

Erythritol production from sugar based feedstocks by Moniliella pollinis using lysate of recycled cells as nutrients source

Biotechnological production of erythritol from industrial substrates such as sugarcane juice and molasses may provide an alternative route for the production of this important platform chemical. In the present study, pure erythritol crystals were produced from sugarcane juice using basidiomycetous fungi Moniliella pollinis in batch and fed batch fermentation. Moniliella cells recovered from the fermentation broth were boiled and the resulting cell lysate was used as the sole source of nitrogen as well as other essential nutrients, including several macro and micronutrients, for erythritol fermentation. In sugarcane juice, Moniliella cells lysate based media resulted in a two-fold increase in erythritol yield and productivity when compared to yeast extract based medium. Maximum of 94.9 g/L erythritol titre with 0.38 g/g yield of total sugar was achieved in fed batch fermentation with sugarcane juice. Downstream processing of fermentation broth resulted in 96 % pure erythritol crystals. Use of Monililella cells lysate based media allowed ethanol to erythritol conversion, resulting in higher overall yield. It is proposed that M. pollinis utilizes ethanol by converting into acetic acid which is subsequently metabolized via TCA cycle. This study demonstrated the potential of sugarcane juice as an industrial feedstock for erythritol production using wild type M. pollinis.

Enhancing erythritol production by wheat straw biochar-incorporated solid-state fermentation of agricultural wastes using defatted Schizochytrium sp. biomass as supplementary feedstock

Defatted Schizochytrium residue was used as a supplementary feedstock for efficiency erythritol production in this study. Microalgae are attractive feedstocks for the microbial process. However, proper enzymatic hydrolysis and toxicity alleviation must be considered for efficient fermentation. A strategy was proposed herein for producing erythritol from enzymatic hydrolysate of the defatted Schizochytrium residue (SRH), resorting to the wheat (Triticum aestivum L.) straw biochar-incorporated solid-state fermentation (SSF) of agricultural wastes to relieve the toxicant inhibition. Enhanced erythritol production (190.5 mg/gds) was achieved in batch SSF supplemented with 4% biochar and 20 % concentrated SRH, which was obtained from the cellulose–protease (1:1) system performed under pH 5.0 and 45 °C for 24 h with 0.8 % (m/v) of enzyme addition. Fed- and repeated-batch fermentation demonstrated enduring high cell viability and improved erythritol yield of 223.2 and 205.4 mg/gds, respectively. Cost analysis suggested high availabilities of raw substrates for erythritol cultivation, which was energy conserving and operable. Moreover, SRH was proven to be an economic alternative feedstock for low-cost erythritol production via the biochar-incorporated SSF.

Erythritol Chemical Structure, Biosynthesis Pathways, Properties, Applications, and Production

Erythritol is a natural four carbon sugar alcohol present in fruits, vegetables, mushrooms and in fermented foods. It is low calorie sweetener manufactured commercially by fermentation using osmophilic yeasts and yeasts-like fungi. Some filamentous fungi and heterofermentative lactic acid bacteria demonstrated on laboratory scale the production of erythritol at lower yield. Erythritol is gaining high market share as natural sweetener with applications in low calorie foods, beverages, and as an additive in combination with high intense zero calorie artificial sweeteners to enhance sweetness, texture, and to mask these artificial sweeteners bitter after taste. Due to increasing demand of erythritol with wide applications in foods, pharmaceuticals, and chemical industries, research activities are focusing on reducing production cost by fermentation conditions optimization. and improve industrial cultures via mutation or genetic engineering to utilize cheap and abundant byproducts such as crude glycerol and lignocellulosic materials as carbon sources in replacement to the costly glucose. Erythritol production with less intermediate metabolites in the fermentation process can be achieved by microbial metabolic pathway engineering. High yield of erythritol with less intermediate metabolites at the end of fermentation process will lead to improve erythritol recovery efficiency with higher yield and specifications.

Knock Down of Erythrulose Kinase (eyk1) Leads to the Enhancement of Erythritol Production in Yarrowia lipolytica Mutant Strain YE4-2

Erythritol is a nearly zero-calorie sweetener, which is in great demand in food and health care industry. Our previous work obtained a Yarrowia lipolytica mutant strain YE4-2 with high erythritol yield. However, its conversion rate of glucose needs further improvement. Erythrulose kinase (eyk1) participates in the early stages of erythritol catabolism; the existence of eyk1 prevents the accumulation of erythritol. In this study, the genetic transformation system of Y. lipolytica YE4-2 was firstly established and the Cre/loxp homologous recombination knockout system was constructed. By using the Cre/loxp system, eyk1 gene was deleted. According to the PCR verification of eyk1 gene, it was preliminarily determined that one allele of eyk1 in this recombinant strain was knocked out. The recombination strain showed an average conversion rate of 48.51%, which was 49.26% higher than that of YE4-2 and the erythritol productivity is increased by 62.26%, which would be a significant improvement in the industrial scale.

Erythritol: Another C4 Platform Chemical in Biomass Refinery.

The potential of erythritol as a platform chemical in biomass refinery is discussed in terms of erythritol production and utilization. Regarding erythritol production, fermentation of sugar or starch has been already commercialized. The shift of the carbon source from glucose to inexpensive inedible waste glycerol is being investigated, which will decrease the price of erythritol. The carbon-based yield of erythritol from glycerol is comparable to or even higher than that from glucose. The metabolic pathway of erythritol biosynthesis has become clarified: erythrose-4-phosphate, which is one of the intermediates in the pentose phosphate pathway, is dephosphorylated and reduced to erythritol. The information about the metabolic pathway may give insights to improve the productivity by bleeding. Regarding erythritol utilization, chemical conversions of erythritol, especially deoxygenation, have been investigated in these days. Erythritol is easily dehydrated to 1,4-anhydroerythritol, which can be also used as the substrate for production of useful C4 chemicals. C–O hydrogenolysis and deoxydehydration using heterogeneous catalysts are effective reactions for erythritol/1,4-anhydroerythritol conversion.

Enhancing the erythritol production by Yarrowia lipolytica from waste oil using loofah sponge as oil-in-water dispersant

Waste oil is an economical alternative carbon resource in Yarrowia-based erythritol production, but the water insolubility limits its further utilization. Loofah sponge (LS), a natural polymer material and accessible agricultural waste, was selected as oil-in-water dispersant in this study. In the oil–erythritol cultivation system with LS addition, efficient oil dispersion and enhanced erythritol production (by ˜30%) were achieved, with high biomass and scarce residual oil in the medium. Up to 60.0 g/L of waste oil could be completely consumed under the effect of LS, resulting to an erythritol yield of 0.76 ± 0.03 g/g oil. Scanning electron microscopy (SEM) images and reusability experiments showed that the LS fiber was well preserved and could be stable for more than five continuous cycles in this process. The changes in activities of the metabolic enzymes suggested an enhanced carbon flux in erythritol synthesis pathway, which was accompanied with an improved oxygen consumption. Moreover, with LS addition, scale-up and fed-batch cultivations was well conducted, up to 114.3 ± 1.8 g/L of erythritol was produced from waste oil when the two cultivation strategies were combined. This study demonstrated an efficient and eco-friendly method for the utilization of waste oily substrates in production of microbial metabolites.

Identification, characterization of two NADPH-dependent erythrose reductases in the yeast Yarrowia lipolytica and improvement of erythritol productivity using metabolic engineering

BackgroundErythritol is a four-carbon sugar alcohol with sweetening properties that is used by the agro-food industry as a food additive. In the yeast Yarrowia lipolytica, the last step of erythritol synthesis involves the reduction of erythrose by specific erythrose reductase(s). In the earlier report, an erythrose reductase gene (YALI0F18590g) from erythritol-producing yeast Y. lipolytica MK1 was identified (Janek et al. in Microb Cell Fact 16:118, 2017). However, deletion of the gene in Y. lipolytica MK1 only resulted in some lower erythritol production but the erythritol synthesis process was still maintained, indicating that other erythrose reductase gene(s) might exist in the genome of Y. lipolytica.ResultsIn this study, we have isolated genes g141.t1 (YALI0D07634g) and g3023.t1 (YALI0C13508g) encoding two novel erythrose reductases (ER). The biochemical characterization of the purified enzymes showed that they have a strong affinity for erythrose. Deletion of the two ER genes plus g801.t1 (YALI0F18590g) did not prevent erythritol synthesis, suggesting that other ER or ER-like enzymes remain to be discovered in this yeast. Overexpression of the newly isolated two genes (ER10 or ER25) led to an average 14.7% higher erythritol yield and 31.2% higher productivity compared to the wild-type strain. Finally, engineering NADPH cofactor metabolism by overexpression of genes ZWF1 and GND1 encoding glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, respectively, allowed a 23.5% higher erythritol yield and 50% higher productivity compared to the wild-type strain. The best of our constructed strains produced an erythritol titer of 190 g/L in baffled flasks using glucose as main carbon source.ConclusionsOur results highlight that in the Y. lipolytica genome several genes encode enzymes able to reduce erythrose into erythritol. The catalytic properties of these enzymes and their cofactor dependency are different from that of already known erythrose reductase of Y. lipolytica. Constitutive expression of the newly isolated genes and engineering of NADPH cofactor metabolism led to an increase in erythritol titer. Development of fermentation strategies will allow further improvement of this productivity in the future.

Novel two-stage solid-state fermentation for erythritol production on okara–buckwheat husk medium

An economical model of two-stage solid state fermentation (SSF) (prefermentation stage with Mucor flavus and in situ erythritol fermentation stage with Yarrowia lipolytica) for enhancing erythritol production was investigated. Buckwheat husk (BH) was utilized as inert support for the first time and okara as the substrate. Morphological properties suggested yeast cells were exposed in adequate oxygen leading to high erythritol yield, and enzyme activities analysis indicated M. flavus and Y. lipolytica grew and cooperated well during the two ferment stages. Maximum erythritol production (143.3 mg/gds) was obtained from okara–BH mixture (5:2, w/w) supplemented with 0.01 g/gds NaCl, with an initial moisture content of 60% and pH of 4.0 for 192 h, while undesired mannitol and citric acid were suppressed. Compared with submerged fermentation, two-stage SSF was short period, energy conserving and operable for erythritol production from insoluble wastes, and this is the first report on erythritol production via SSF.

Effects of osmotic pressure and pH on citric acid and erythritol production from waste cooking oil by Yarrowia lipolytica.

Erythritol and citric acid could be produced from waste cooking oil (WCO) by Yarrowia lipolytica under different medium conditions, and osmotic pressure together with pH were considered to be the critical factors in this process. High osmotic pressure (2.76osmol/L) combined with low pH (pH 3.0) promoted the highest yield of erythritol (21.8g/L) accompanied by low-producing citric acid (2.5g/L). By contrast, the highest citric acid biosynthesis (12.6g/L) was detected under a pH of 6.0 and an osmotic pressure of 0.75osmol/L, when only 4.0g/L of erythritol was yielded. Moreover, lipase activities in these two media were also detected, and pH 3.0-OP 2.76 was supposed to be more beneficial to lipase activity. Biochemical pathways involved in the biosynthesis of erythritol and citric acid were subsequently investigated, and the products yielded from WCO were assumed to be correlated with the activities of transketolase, erythrose reductase, citrate synthase, and glycerol kinase. However, RT-PCR analysis revealed that mRNA levels of these enzymes did not significantly differ, confirming that metabolic flux regulations of erythritol and citric acid mostly took place at the post-transcriptional level.

Erythritol production by Yarrowia lipolytica from okara pretreated with the in-house enzyme pools of fungi

Okara (soybean residue) is an ideal erythritol feedstock due to its low price and high-nutrient content. Fungal-fermentations were carried out in okara using in-house enzyme pools generated by Mucor flavus or Trichoderma reesei to make okara more accessibility in the subsequent erythritol production using Yarrowia lipolytica. Mucor-fermented okara produced a high erythritol yield because of its special component and micromorphology. Five days is the optimal period for Mucor fermentation. Different fermentation modes were compared in terms of erythritol production and yield. The concentration of Mucor-fermented okara in erythritol fermentation medium was optimal at 30.0g/L. Moreover, 40.0g/L NaCl was added as the osmotic regulator. No extra ingredient was needed during this process. Results of 5-L fermentations showed that an erythritol titer of 14.7g/L, with a yield of 0.49g/g okara was obtained. These findings indicated that Mucor-fermented okara was an economically alternative feedstock for low-cost erythritol production.

Erythritol production by Yarrowia lipolytica mutant strain M53 generated through atmospheric and room temperature plasma mutagenesis.

Mutants of Yarrowia lipolytica with high erythritol production were generated through an atmospheric and room temperature plasma (ARTP) mutation system. Among these mutants, Y. lipolytica M53 exhibited the highest erythritol yield. In a batch culture, M53 produced 64.8g/L erythritol from 100g/L glycerol. The yields of byproducts (e.g. mannitol, arabitol, and α-ketoglutaric acid) were low, and the mechanisms underlying these changes were examined by measuring enzyme activities in the pentose phosphate pathway. Up to 145.2g/L erythritol was produced by M53 from 200g/L of glycerol, and erythritol accumulation was promoted by 3.7mg/L of Cu2+, 10.15mg/L of Mn2+, and 30.37g/L of NaCl. Fed-batch cultivation of M53 in a 5-L fermentor produced 169.3g/L erythritol with low levels of byproducts within 168h. This finding confirmed the potential of M53 as an erythritol producer on a commercial scale.

A novel strain of Yarrowia lipolytica as a platform for value-added product synthesis from glycerol.

BackgroundIncreasing interest of non-conventional yeasts has been observed for many years due to their biochemical characteristics and potential applications. Well-studied, oleaginous yeast Y. lipolytica is an attractive host for converting a low-cost glycerol, into value-added products such as erythritol (sweetener) or citric acid. Glycerol is an important renewable feedstock and is the main co-product of biodiesel production, which is nowadays applied on a large commercial scale. To this end, we engineered the yeast Y. lipolytica to increase the productivity of this strain.ResultsIn this light, we enhanced glycerol assimilation by over-expression of the YALI0F00484g gene encoding glycerol kinase (GK) and gene YALI0B02948g encoding glycerol-3-P dehydrogenase (GDH). The modified strains have been tested for glycerol consumption rate and erythritol and citric acid synthesis under various conditions. Here, we show that the overexpression of GK and GDH, increased glycerol consumption resulting in rapid erythritol and citric acid synthesis. Next, we combined the two genes in the tandem gene construct for the simultaneous co-expression of GK and GDH, which further increased the desired product synthesis. The glycerol consumption was explored in a 5-L bioreactor and the engineered strains were able to utilize 150 g/L glycerol within 44–48 hours. The erythritol productivity for GK overexpression and co-expression of GK and DGH was 24 and 35 %, respectively, over the control strain. Moreover, we established conditions for the production of citric acid at pH 3.0, the engineered strains increased citric acid production 14-fold over the control.ConclusionThis work demonstrates the excellent capacity of the engineered strains as a starting platform for further modification for broad-range value-added product biosynthesis from glycerol. This study presents the highest reported titer citric acid at low pH to date. The process parameters such as productivity and yield of erythritol and citric acid were significantly elevated, what is valuable for industrial applications.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0593-z) contains supplementary material, which is available to authorized users.

Optimization of a low-cost hyperosmotic medium and establishing the fermentation kinetics of erythritol production by Yarrowia lipolytica from crude glycerol

ABSTRACTThe production of erythritol by Yarrowia lipolytica from low-cost substitutable substrates for high yield was investigated. Crude glycerol, urea, and NaCl related to osmotic pressure were the most significant factors affecting erythritol production. An artificial neural network model and genetic algorithm were used to search the optimal composition of the significant factors and locate the resulting erythritol yield. Medium with 232.39 g/L crude glycerol, 1.57 g/L urea, and 31.03 g/L NaCl led to predictive maximum erythritol concentration of 110.7 g/L. The erythritol concentration improved from 50.4 g/L to 109.2 g/L with the optimized medium, which was reproducible. Erythritol fermentation kinetics were investigated in a batch system. Multistep fermentation kinetic models with hyperosmotic inhibitory effects were developed. The resulting mathematical equations provided a good description of temporal variations such as microbial growth (X), substrate consumption (S), and product formation (P) in erythritol fermentation. The accordingly derived model is the first reported model for fermentative erythritol production from glycerol, providing useful information to optimize the growth of Y. lipolytica and contributing visual description for the erythritol fermentation process under high osmotic pressure, as well as improvement of productivity and efficiency.

Erythritol production by Moniliella megachiliensis using nonrefined glycerol waste as carbon source.

The number of naphtha plants is being reduced due to a worldwide shift in energy sources. Consequently, a shortage of chemical materials heavily dependent on naphtha-oil, especially C4 compounds such as butene and butane-diol, is an urgent issue in chemical manufacturing. Erythritol is a rare C4 compound produced by fermentation processes using glucose as the carbon source. Since erythritol is considerably more expensive than hydrocarbons derived from naphtha-oil, a reduction in its cost is critical. We found that Moniliella megachiliensis, a highly osmotolerant yeast strain, can utilize nonrefined glycerol waste derived from palm oil or beef tallow and convert it to erythritol. Cell growth on glycerol was almost the same as on glucose, and the cells could grow in up to 300mgml(-1) glycerol. When 200mgml(-1) nonrefined glycerol was supplied, the yield of erythritol from the glycerol was approx. 60%, which is slightly higher than that obtained using glucose. The cost of glycerol waste is considerably lower than that of glucose. Thus, the conversion of glycerol waste into valuable erythritol, proposed here, is attractive and promising from the viewpoint of ensuring a supply of C4 hydrocarbons and utilizing a waste natural resource. A shortage of C4 hydrocarbon depending much on naptha-oil has become urgent problem due to rapid reduction of naphtha plants together with global energy revolution. Erythritol, obtained by fermentation, is a rare C4 polyol that can be converted to C4 hydrocarbons. Erythritol is considerably expensive than hydrocarbons, a reduction in cost is critical issue. To meet this, we proposed to utilize low-cost glycerol waste from bio-diesel fuel as a carbon source. Moniliella megachiliensis successfully converted glycerol waste to erythritol. This proposal is promising to obtain C4 hydrocarbon substitute, and concomitantly to dispose a large amount of glycerol waste discharged.