L(+) Lactate production from carbohydrates and lignocellulosic materials by Rhizopus oryzae UMIP 4.77

The lactate excretion by Rhizopus oryzae on various carbohydrates was studied in order to assess the potential of lactate production from raw materials. Six collection strains were tested on ten commercial carbohydrates i.e. glucose, xylose, glycerol, sucrose, lactose, cellobiose, inulin, starch, cellulose and fructose in flask or stirred-tank bioreactor. On glucose and xylose, lactate was produced by R. oryzae UMIP 4.77 at 73 and 8 gL^?1 respectively, indicating that lignocellulosic materials could be used as possible raw substrates. Two lignocellulosic substrates were therefore experimented in stirred-tank bioreactor with R. oryzae UMIP 4.77. The first one was hemicellulosic material, which is a concentrated C6 and C5 sugar solution resulting from washing of a steamed wheat straw sample. The second was cellulosic material, which is a partially-hydrolyzed unbleached pulp paper. In a simultaneous saccharification fermentation process, a final production of 24.1 gL^?1 of lactate was obtained from cellulosic material.     

Metabolic engineering of Rhizopus oryzae: Effects of overexpressing fumR gene on cell growth and fumaric acid biosynthesis from glucose

Fumaric acid is a dicarboxylic acid used extensively in synthetic resins, food acidulants, and other applications, including oil field fluids and esters. The filamentous fungus Rhizopus oryzae is known for its ability to produce and accumulate high levels of fumaric acid under aerobic conditions. In this work, the overexpression of native fumarase encoded by fumR and its effect on fumaric acid production in R. oryzae were investigated. Three plasmids containing the endogenous fumR gene were constructed and used to transform R. oryzae, and all transformants showed significantly increased fumarase activity during both the seed culture (growth) and fermentation (fumaric acid production) stages. However, fumarase overexpression in R. oryzae yielded more malic acid, instead of fumaric acid, in the fermentation because the overexpressed fumarase also catalyzed the hydration of fumaric acid to malic acid. The results suggested that the overexpressed fumarase, encoded by fumR, by itself was not responsible for the over-production of fumaric acid in R. oryzae.     

Continuous succinic acid production from xylose by <Emphasis Type="Italic">Actinobacillus succinogenes</Emphasis>

Continuous, anaerobic fermentations of D-xylose were performed by Actinobacillus succinogenes 130Z in a custom, biofilm reactor at dilution rates of 0.05, 0.10 and 0.30 h^?1. Succinic acid yields on xylose (0.55–0.68 g g^?1), titres (10.9–29.4 g L^?1) and productivities (1.5–3.4 g L^?1 h^?1) were lower than those of a previous study on glucose, but product ratios (succinic acid/acetic acid = 3.0–5.0 g g^?1) and carbohydrate consumption rates were similar. Also, mass balance closures on xylose were up to 18.2 % lower than those on glucose. A modified HPLC method revealed pyruvic acid excretion at appreciable concentrations (1.2–1.9 g L^?1) which improved the mass balance closure by up to 16.8 %. Furthermore, redox balances based on the accounted xylose consumed and the excreted metabolites, indicated an overproduction of reducing power. The oxidative pentose phosphate pathway was shown to be a plausible source of the additional reducing power.     

Enhancing ethanol production from cellulosic sugars using <Emphasis Type="Italic">Scheffersomyces (Pichia) stipitis</Emphasis>

Studies were performed on the effect of CaCO₃ and CaCl₂ supplementation to fermentation medium for ethanol production from xylose, glucose, or their mixtures using Scheffersomyces (Pichia) stipitis. Both of these chemicals were found to improve maximum ethanol concentration and ethanol productivity. Use of xylose alone resulted in the production of 20.68 ± 0.44 g L^?1 ethanol with a productivity of 0.17 ± 0.00 g L^?1 h^?1, while xylose plus 3 g L^?1 CaCO₃ resulted in the production of 24.68 ± 0.75 g L^?1 ethanol with a productivity of 0.21 ± 0.01 g L^?1 h^?1. Use of xylose plus glucose in combination with 3 g L^?1 CaCO₃ resulted in the production of 47.37 ± 0.55 g L^?1 ethanol (aerobic culture), thus resulting in an ethanol productivity of 0.39 ± 0.00 g L^?1 h^?1. These values are 229 % of that achieved in xylose medium. Supplementation of xylose and glucose medium with 0.40 g L^?1 CaCl₂ resulted in the production of 44.84 ± 0.28 g L^?1 ethanol with a productivity of 0.37 ± 0.02 g L^?1 h^?1. Use of glucose plus 3 g L^?1 CaCO₃ resulted in the production of 57.39 ± 1.41 g L^?1 ethanol under micro-aerophilic conditions. These results indicate that supplementation of cellulosic sugars in the fermentation medium with CaCO₃ and CaCl₂ would improve economics of ethanol production from agricultural residues.     

Evaluation of ethanol production by a new isolate of yeast during fermentation in synthetic medium and sugarcane bagasse hemicellulosic hydrolysate

A new xylose fermenting yeast was isolated from over-ripe banana by enrichment in xylose-containing medium. The phylogenetic analysis of ITS1-5.8S-ITS2 region sequences of ribosomal RNA of isolate BY2 revealed that it shows affiliation to genus Pichia and clades with Pichia caribbica. In batch fermentation, Pichia strain BY2 fermented xylose, producing 15 g l^?1 ethanol from 30 g l^?1 xylose under shaking conditions at 28°C, with ethanol yield of 0.5 g g^?1 and volumetric productivity of 0.31 g l^?1 h^?1. The optimum pH range for ethanol production from xylose by Pichia strain BY2 was 5–7. Pichia strain BY2 also produced 6.08 g l^?1 ethanol from 30 g l^?1 arabinose. Pichia strain BY2 can utilize sugarcane bagasse hemicellulose acid hydrolysate for alcohol production, efficiency of fermentation was improved by neutralization, and sequential use of activated charcoal adsorption method. Percent total sugar utilized and ethanol yield for the untreated hydrolysate was 17.14% w/v and 0.33 g g^?1, respectively, compared with 66.79% w/v and 0.45 g g^?1, respectively, for treated hemicellulose acid hydrolysate. This new yeast isolate showed ethanol yield of 0.45 g g^?1 and volumetric productivity of 0.33 g l^?1 h^?1 from sugarcane bagasse hemicellulose hydrolysate detoxified by neutralization and activated charcoal treatment, and has potential application in practical process of ethanol production from lignocellulosic hydrolysate.     

Evaluation of hexose and pentose in pre-cultivation of <Emphasis Type="Italic">Candida guilliermondii</Emphasis> on the key enzymes for xylitol production in sugarcane hemicellulosic hydrolysate

The evaluation of hexose and pentose in pre-cultivation of Candida guilliermondii FTI 20037 yeast on xylose reductase (XR) and xylitol dehydrogenase (XDH) enzymes activities was performed during fermentation in sugarcane bagasse hemicellulosic hydrolysate. The xylitol production was evaluated by using cells previously growth in 30.0 gl^?1 xylose, 30.0 gl^?1 glucose and in both sugars mixture (30.0 gl^?1 xylose and 2.0 gl^?1 glucose). The vacuum evaporated hydrolysate (80 gl^?1) was detoxificated by ion exchange resin (A-860S; A500PS and C-150-Purolite^®). The total phenolic compounds and acetic acid were 93.0 and 64.9%, respectively, removed by the resin hydrolysate treatment. All experiments were carried out in Erlenmeyer flasks at 200 rpm, 30°C. The maximum XR (0.618 Umg _Prot ^?1 ) and XDH (0.783 Umg _Prot ^?1 ) enzymes activities was obtained using inoculum previously growth in both sugars mixture. The highest cell concentration (10.6 gl^?1) was obtained with inoculum pre-cultivated in the glucose. However, the xylitol yield and xylitol volumetric productivity were favored using the xylose as carbon source. In this case, it was observed maximum xylose (81%) and acetic acid (100%) consumption. It is very important to point out that maximum enzymatic activities were obtained when the mixture of sugars was used as carbon source of inoculum, while the highest fermentative parameters were obtained when xylose was used.     

A novel isolate of <Emphasis Type="Italic">Clostridium butyricum</Emphasis> for efficient butyric acid production by xylose fermentation

Bacterial fermentation of lignocellulose has been regarded as a sustainable approach to butyric acid production. However, the yield of butyric acid is hindered by the conversion efficiency of hydrolysate xylose. A mesophilic alkaline-tolerant strain designated as Clostridium butyricum B10 was isolated by xylose fermentation with acetic and butyric acids as the principal liquid products. To enhance butyric acid production, performance of the strain in batch fermentation was evaluated with various temperatures (20–47 °C), initial pH (5.0–10.0), and xylose concentration (6–20 g/L). The results showed that the optimal temperature, initial pH, and xylose concentration for butyric acid production were 37 °C, 9.0, and 8.00 g/L, respectively. Under the optimal condition, the yield and specific yield of butyric acid reached about 2.58 g/L and 0.36 g/g xylose, respectively, with 75.00% butyric acid in the total volatile fatty acids. As renewable energy, hydrogen was also collected from the xylose fermentation with a yield of about 73.86 mmol/L. The kinetics of growth and product formation indicated that the maximal cell growth rate (μ _m ) and the specific butyric acid yield were 0.1466 h^?1 and 3.6274 g/g cell (dry weight), respectively. The better performance in xylose fermentation showed C. butyricum B10 a potential application in efficient butyric acid production from lignocellulose.     

Implementation of a transhydrogenase-like shunt to counter redox imbalance during xylose fermentation in Saccharomyces cerevisiae

Three enzymes responsible for the transhydrogenase-like shunt, including malic enzyme (encoded by MAE1), malate dehydrogenase (MDH2), and pyruvate carboxylase (PYC2), were overexpressed to regulate the redox state in xylose-fermenting recombinant Saccharomyces cerevisiae. The YPH499XU/MAE1 strain was constructed by overexpressing native Mae1p in the YPH499XU strain expressing xylose reductase and xylitol dehydrogenase from Scheffersomyces stipitis, and native xylulokinase. Analysis of the xylose fermentation profile under semi-anaerobic conditions revealed that the ethanol yield in the YPH499XU/MAE1 strain (0.38?±?0.01 g g^?1 xylose consumed) was improved from that of the control strain (0.31?±?0.01 g g^?1 xylose consumed). Reduced xylitol production was also observed in YPH499XU/MAE1, suggesting that the redox balance was altered by Mae1p overexpression. Analysis of intracellular metabolites showed that the redox imbalance during xylose fermentation was partly relieved in the transformant. The specific ethanol production rate in the YPH499XU/MAE1–MDH2 strain was 1.25-fold higher than that of YPH499XU/MAE1 due to the additional overexpression of Mdh2p, whereas the ethanol yield was identical to that of YPH499XU/MAE1. The specific xylose consumption rate was drastically increased in the YPH499XU/MAE1–MDH2–PYC2 strain. However, poor ethanol yield as well as increased production of xylitol was observed. These results demonstrate that the transhydrogenase function implemented in S. cerevisiae can regulate the redox state of yeast cells.     

Lactic acid production from xylose by the fungus Rhizopus oryzae

Lignocellulosic biomass is considered nowadays to be an economically attractive carbohydrate feedstock for large-scale fermentation of bulk chemicals such as lactic acid. The filamentous fungus Rhizopus oryzae is able to grow in mineral medium with glucose as sole carbon source and to produce optically pure l(+)-lactic acid. Less is known about the conversion by R. oryzae of pentose sugars such as xylose, which is abundantly present in lignocellulosic hydrolysates. This paper describes the conversion of xylose in synthetic media into lactic acid by ten R. oryzae strains resulting in yields between 0.41 and 0.71 g g⁻¹. By-products were fungal biomass, xylitol, glycerol, ethanol and carbon dioxide. The growth of R. oryzae CBS 112.07 in media with initial xylose concentrations above 40 g l⁻¹ showed inhibition of substrate consumption and lactic acid production rates. In case of mixed substrates, diauxic growth was observed where consumption of glucose and xylose occurred subsequently. Sugar consumption rate and lactic acid production rate were significantly higher during glucose consumption phase compared to xylose consumption phase. Available xylose (10.3 g l⁻¹) and glucose (19.2 g l⁻¹) present in a mild-temperature alkaline treated wheat straw hydrolysate was converted subsequently by R. oryzae with rates of 2.2 g glucose l⁻¹ h⁻¹ and 0.5 g xylose l⁻¹ h⁻¹. This resulted mainly into the product lactic acid (6.8 g l⁻¹) and ethanol (5.7 g l⁻¹).     

Effect of controlled oxygen limitation on Candida shehatae physiology for ethanol production from xylose and glucose

Carbon distribution and kinetics of Candida shehatae were studied in fed-batch fermentation with xylose or glucose (separately) as the carbon source in mineral medium. The fermentations were carried out in two phases, an aerobic phase dedicated to growth followed by an oxygen limitation phase dedicated to ethanol production. Oxygen limitation was quantified with an average specific oxygen uptake rate (OUR) varying between 0.30 and 2.48 mmolO₂ g dry cell weight (DCW)^?1 h^?1, the maximum value before the aerobic shift. The relations among respiration, growth, ethanol production and polyol production were investigated. It appeared that ethanol was produced to provide energy, and polyols (arabitol, ribitol, glycerol and xylitol) were produced to reoxidize NADH from assimilatory reactions and from the co-factor imbalance of the two-first enzymatic steps of xylose uptake. Hence, to manage carbon flux to ethanol production, oxygen limitation was a major controlled parameter; an oxygen limitation corresponding to an average specific OUR of 1.19 mmolO₂ g DCW^?1 h^?1 allowed maximization of the ethanol yield over xylose (0.327 g g^?1), the average productivity (2.2 g l^?1 h^?1) and the ethanol final titer (48.81 g l^?1). For glucose fermentation, the ethanol yield over glucose was the highest (0.411 g g^?1) when the specific OUR was low, corresponding to an average specific OUR of 0.30 mmolO₂ g DCW^?1 h^?1, whereas the average ethanol productivity and ethanol final titer reached the maximum values of 1.81 g l^?1 h^?1 and 54.19 g l^?1 when the specific OUR was the highest.     

Enrichment of biologically active 18-β glycyrrhetinic acid in Glycyrrhiza glabra root by solid state fermentation

This paper describes the in situ bioconversion of glycyrrhizin of Glycyrrhiza glabra root to 18-β glycyrrhetinic acid by solid state fermentation. Fermentation was carried out with two different fungal strains, Penicillium chrysogenum and Rhizopus oryzae. The solid state fermentation was carried out under stationary state and under rotating state. Penicillium chrysogenum is a better producer of 18-β glycyrrhetinic acid than Rhizopus oryzae. The induced P. chrysogenum seed culture produces higher 18-β glycyrrhetinic acid with 2.955 mg g^?1 and maximum β-glucuronidase activity of 3,583.8 U ml^?1 under stationary solid state fermentation. The mycelium growth and bioconversion rate is highest at pH of 5.5 and 4.5, respectively. G. glabra root supplemented with a solution of dextrose 9 g l^?1, MnSO₄?·?H₂O 3 g l^?1 and (NH₄)₂SO₄ 0.540 g l^?1 produces 48.580 mg of 18-β glycyrrhetinic acid per gram of G. glabra root, i.e. 86.74 % bioconversion by P. chrysogenum in 96 h under stationary state solid state fermentation.     

Xylan-hydrolyzing thermotolerant <Emphasis Type="Italic">Candida tropicalis</Emphasis> HNMA-1 for bioethanol production from sugarcane bagasse hydrolysate

Sugarcane bagasse is one of the low-cost substrates used for bioethanol production. In order to solubilize sugars in hemicelluloses like xylan, a new thermotolerant isolate of Candida tropicalis HNMA-1 with xylan-hydrolyzing ability was identified and characterized. The strain showed relative tolerance to high temperature. Our results demonstrated 0.211 IU ml^?1 xylanase activity at 40 °C compared to 0.236 IU ml^?1 at 30 °C. The effect of high temperature on the growth and fermentation of xylose and sugarcane bagasse hydrolysate were also investigated. In both xylose or hydrolysate medium, increased growth was recorded at 40 °C. Meanwhile, the efficiency of ethanol fermentation was adversely affected by temperature since yields of 0.088 g g^?1 and 0.076 g g^?1 in the xylose medium, in addition to 0.090 g g^?1 and 0.078 g g^?1 in the hydrolysate medium were noticed at 30 °C and 40 °C, respectively. Inhibitory compounds in the hydrolysate medium demonstrated negative effects on fermentation and productivity, with maximum ethanol concentration attained after 48 h in the hydrolysate, as opposed to 24 h in the xylose medium. Our data show that the newly thermotolerant isolate, C. tropicalis HNMA-1, is able to efficiently ferment xylose and hydrolysate, and also has the capacity for application in ethanol production from hemicellulosic sources.     

Kinetics of growth and ethanol formation from a mix of glucose/xylose substrate by Kluyveromyces marxianus UFV-3

The fermentation of both glucose and xylose is important to maximize ethanol yield from renewable biomass feedstocks. In this article, we analyze growth, sugar consumption, and ethanol formation by the yeast Kluyveromyces marxianus UFV-3 using various glucose and xylose concentrations and also under conditions of reduced respiratory activity. In almost all the conditions analyzed, glucose repressed xylose assimilation and xylose consumption began after glucose had been exhausted. A remarkable difference was observed when mixtures of 5 g L^?1 glucose/20 g L^?1 xylose and 20 g L^?1 glucose/20 g L^?1 xylose were used. In the former, the xylose consumption began immediately after the glucose depletion. Indeed, there was no striking diauxic phase, as observed in the latter condition, in which there was an interval of 30 h between glucose depletion and the beginning of xylose consumption. Ethanol production was always higher in a mixture of glucose and xylose than in glucose alone. The highest ethanol concentration (8.65 g L^?1) and cell mass concentration (4.42 g L^?1) were achieved after 8 and 74 h, respectively, in a mixture of 20 g L^?1 glucose/20 g L^?1 xylose. When inhibitors of respiration were added to the medium, glucose repression of xylose consumption was alleviated completely and K. marxianus was able to consume xylose and glucose simultaneously.     

Production of aglycone protopanaxatriol from ginseng root extract using Dictyoglomus turgidum β-glycosidase that specifically hydrolyzes the xylose at the C-6 position and the glucose in protopanaxatriol-type ginsenosides

The hydrolytic activity of a recombinant β-glycosidase from Dictyoglomus turgidum that specifically hydrolyzed the xylose at the C-6 position and the glucose in protopanaxatriol (PPT)-type ginsenosides followed the order Rf > Rg₁ > Re > R₁ > Rh₁ > R₂. The production of aglycone protopanaxatriol (APPT) from ginsenoside Rf was optimal at pH 6.0, 80 °C, 1 mg ml^?1 Rf, and 10.6 U ml^?1 enzyme. Under these conditions, D. turgidum β-glycosidase converted ginsenoside R₁ to APPT with a molar conversion yield of 75.6 % and a productivity of 15 mg l^?1 h^?1 after 24 h by the transformation pathway of R₁ → R₂ → Rh₁ → APPT, whereas the complete conversion of ginsenosides Rf and Rg₁ to APPT was achieved with a productivity of 1,515 mg l^?1 h^?1 after 6.6 h by the pathways of Rf → Rh₁ → APPT and Rg₁ → Rh₁ → APPT, respectively. In addition, D. turgidum β-glycosidase produced 0.54 mg ml^?1 APPT from 2.29 mg ml^?1 PPT-type ginsenosides of Panax ginseng root extract after 24 h, with a molar conversion yield of 43.2 % and a productivity of 23 mg l^?1 h^?1, and 0.62 mg ml^?1 APPT from 1.35 mg ml^?1 PPT-type ginsenosides of Panax notoginseng root extract after 20 h, with a molar conversion yield of 81.2 % and a productivity of 31 mg l^?1 h^?1. This is the first report on the APPT production from ginseng root extract. Moreover, the concentrations, yields, and productivities of APPT achieved in the present study are the highest reported to date.     

Enhanced production of poly(lactate-co-3-hydroxybutyrate) from xylose in engineered Escherichia coli overexpressing a galactitol transporter

Poly(lactate-co-3-hydroxybutyrate) (P(LA-co-3HB)) was previously produced from xylose in engineered Escherichia coli. The aim of this study was to increase the polymer productivity and LA fraction in P(LA-co-3HB) using two metabolic engineering approaches: (1) deletions of competing pathways to lactate production and (2) overexpression of a galactitol transporter (GatC), which contributes to the ATP-independent xylose uptake. Engineered E. coli mutants (ΔpflA, Δpta, ΔackA, ΔpoxB, Δdld, and a dual mutant; ΔpflA?+?Δdld) and their parent strain, BW25113, were grown on 20 g l^?1 xylose for P(LA-co-3HB) production. The single deletions of ΔpflA, Δpta, and Δdld increased the LA fraction (58–66 mol%) compared to BW25113 (56 mol%). In particular, the ΔpflA?+?Δdld strain produced P(LA-co-3HB) containing 73 mol% LA. Furthermore, GatC overexpression increased both polymer yields and LA fractions in ΔpflA, Δpta, and Δdld mutants, and BW25113. The ΔpflA?+?gatC strain achieved a productivity of 8.3 g l^?1, which was 72 % of the theoretical maximum yield. Thus, to eliminate limitation of the carbon source, higher concentration of xylose was fed. As a result, BW25113 harboring gatC grown on 40 g l^?1 xylose reached the highest P(LA-co-3HB) productivity of 14.4 g l^?1. On the other hand, the ΔpflA?+?Δdld strain grown on 30 g l^?1 xylose synthesized 6.4 g l^?1 P(LA-co-3HB) while maintaining the highest LA fraction (73 mol%). The results indicated the usefulness of GatC for enhanced production of P(LA-co-3HB) from xylose, and the gene deletions to upregulate the LA fraction in P(LA-co-3HB). The polymers obtained had weight-averaged molecular weights in the range of 34,000–114,000.     

High yield production of four-carbon dicarboxylic acids by metabolically engineered <Emphasis Type="Italic">Escherichia coli</Emphasis>

Several metabolic engineered Escherichia coli strains were constructed and evaluated for four-carbon dicarboxylic acid production. Fumarase A, fumarase B and fumarase C single, double and triple mutants were constructed in a ldhA adhE mutant background overexpressing the pyruvate carboxylase from Lactococcus lactis. All the mutants produced succinate as the main four-carbon (C4) dicarboxylic acid product when glucose was used as carbon source with the exception of the fumAC and the triple fumB fumAC deletion strains, where malate was the main C4-product with a yield of 0.61–0.67 mol (mole glucose)^?1. Additionally, a mdh mutant strain and a previously engineered high-succinate-producing strain (SBS550MG-Cms pHL413-Km) were investigated for aerobic malate production from succinate. These strains produced 40.38 mM (5.41 g/L) and 50.34 mM (6.75 g/L) malate with a molar yield of 0.53 and 0.55 mol (mole succinate)^?1, respectively. Finally, by exploiting the high-succinate production capability, the strain SBS550MG-Cms243 pHL413-Km showed significant malate production in a two-stage process from glucose. This strain produced 133 mM (17.83 g/L) malate in 47 h, with a high yield of 1.3 mol (mole glucose)^?1 and productivity of 0.38 g L^?1 h^?1.     

Polyhydroxyalkanoate biosynthesis and simultaneous remotion of organic inhibitors from sugarcane bagasse hydrolysate by Burkholderia sp.

Burkholderia sp. F24, originally isolated from soil, was capable of growth on xylose and removed organic inhibitors present in a hemicellulosic hydrolysate and simultaneously produced poly-3-hydroxybutyrate (P3HB). Using non-detoxified hydrolysate, Burkholderia sp. F24 reached a cell dry weight (CDW) of 6.8 g L^?1, containing 48 % of P3HB and exhibited a volumetric productivity (P_P3HB) of 0.10 g L^?1 h^?1. Poly-3-hydroxybutyrate-co-3-hydroxyvalerate copolymers (P3HB-co-3HV) were produced using xylose and levulinic acid (LA) as carbon sources. In shake flask cultures, the 3HV content in the copolymer increased from 9 to 43 mol% by adding LA from 1.0 to 5.0 g L^?1. In high cell density cultivation using concentrated hemicellulosic hydrolysate F24 reached 25.04 g L^?1 of CDW containing 49 % of P3HB and P_P3HB of 0.28 g L^?1 h^?1. Based on these findings, second-generation ethanol and bioplastics from sugarcane bagasse is proposed.     

Efficient production of lactic acid from sucrose and corncob hydrolysate by a newly isolated <Emphasis Type="Italic">Rhizopus oryzae</Emphasis> GY18

The aim of this study is to investigate production of l-lactic acid from sucrose and corncob hydrolysate by the newly isolated R. oryzae GY18. R. oryzae GY18 was capable of utilizing sucrose as a sole source, producing 97.5 g l⁻¹ l-lactic acid from 120 g l⁻¹ sucrose. In addition, the strain was also efficiently able to utilize glucose and/or xylose to produce high yields of l-lactic acid. It was capable of producing up to 115 and 54.2 g l⁻¹ lactic acid with yields of up to 0.81 g g⁻¹ glucose and 0.90 g g⁻¹ xylose, respectively. Corncob hydrolysates obtained by dilute acid hydrolysis and enzymatic hydrolysis of the cellulose-enriched residue were used for lactic acid production by R. oryzae GY18. A yield of 355 g lactic acid per kg corncobs was obtained after 72 h incubation. Therefore, sucrose and corncobs could serve as potential sources of raw materials for efficient production of lactic acid by R. oryzae GY18.