Simultaneous lactic acid and xylitol production from vine trimming wastes

Hemicellulosic hydrolyzates from vineshoot trimmings obtained by dilute sulfuric acid hydrolysis were evaluated for xylitol production by Debaryomyces hansenii NRRL Y‐7426. Bioconversion was not efficient, however, since a mixture of products (mainly ethanol) was achieved. Taking into account that hexoses (such as glucose or mannose) can inhibit xylose metabolism by repression and inactivation of the xylose transport system or catabolic enzymes and that these hemicellulosic hydrolyzates are characterized by a high glucose concentration, a novel technology was developed, sequentially transforming glucose into lactic acid by Lactobacillus rhamnosus followed by fermentation of xylose into xylitol by Debaryomyces hansenii after L. rhamnosus removal by microfiltration. Optimal conditions were achieved using detoxified concentrated hemicellulosic hydrolyzates, after CaCO₃ addition in both stages of fermentation and using nitrogen purges after sampling in order to reduce the oxygen dissolved. Under these conditions 31.5 g lactic acid L^?1 (Q_LA = 1.312 g L^?1 h^?1 and Y_LA/S = 0.93 g g^?1) and 27.5 g xylitol L^?1 (Q_Xylitol = 0.458 g L^?1 h^?1 and Y_Xylitol/S = 0.53 g g^?1) were produced. Finally, lactic acid was selectively recovered using the resin Amberlite IRA 400 (0.0374 g of lactic acid g^?1 of dry resin), allowing a further recovery of xylitol by sequential stages of adsorption, concentration, ethanol precipitation, concentration and crystallization to obtain food‐grade xylitol according to a developed process. Copyright © 2007 Society of Chemical Industry     

Modelling of the hydrolysis of sorghum straw at atmospheric pressure

Sorghum straw is a renewable, cheap and widespread resource. The acid hydrolysis of sorghum straw to obtain xylose solutions could be a good alternative for this abundant resource. The H₂SO₄ hydrolysis of sorghum straw at two different temperatures (80 and 100 °C) and three H₂SO₄ concentrations (2, 4 and 6%) using a solid/liquid ratio of 1:10 (w/w) was studied. Kinetic parameters of mathematical models for predicting the concentrations of xylose, glucose, acetic acid and furfural were determined. The activation energy of the release reaction was 183.3 kJ mol^?1 for xylose and 185.8 kJ mol^?1 for glucose. The optimal conditions found were 6% H₂SO₄ at 100 °C for 60 min, which allow one to obtain a solution with 18.27 g xylose l^?1, 6.78 g glucose l^?1, 0.7 g furfural l^?1 and 1.35 g acetic acid l^?1. It is concluded that this process has potential for utilisation of this renewable lignocellulosic resource. © 2002 Society of Chemical Industry     

Effect of added glucose and xylose on the fermentation of perennial ryegrass silage inoculated with Lactobacillus plantarum

Perennial ryegrass (Lolium perenne L) was ensiled in laboratory silos after addition of glucose or xylose at rates of 0, 25, 35 and 45 g kg^?1 fresh grass. In addition, an inoculum of Lactobacillus plantarum, supplying 10⁶ organisms g^?1 fresh grass, was applied to all treatments. Silos were opened after 7, 21 and 100 days and the silage was subjected to chemical and microbiological analysis. AH silages were well fermented with pHs between 3·60 and 3·70 and low NH₃-N concentrations (<95 g kg^?1 total nitrogen) and an absence of butyric acid. Glucose was virtually completely consumed within 21 days but 0·30–0·50 of the xylose doses remained after 100 days. Lactic acid concentrations were not increased by the addition of sugars, but the glucose treatments were associated with very high concentrations of ethanol, 60–100 g kg^?1 DM, and the xylose additions produced very high concentrations of acetic acid, 60–135 g kg^?1 DM. Most(>0·80) of the glucose that disappeared could be accounted for in ethanol formation but the xylose consumed could be accounted for only if the lactic acid produced in its fermentation was metabolised further to acetic acid; indeed, for the two higher doses of xylose, the concentrations of lactic acid were reduced from the control value of 177 g kg^?1 DM to 140 and 120 g kg^?1 DM, respectively. The results indicate that the provision of extra sugar, as hexose or pentose, allows yeasts to assume a more prominent role in the fermentation with consequent wasteful fermentation of sugars. Furthermore, the suggestion is that xylose may indirectly, via a stimulation of lactate-assimilating yeasts, encourage further metabolism of lactic acid to acetic acid.     

Integral utilisation of barley husk for the production of food additives

A new and effective chemical–biotechnological process for the global utilisation of barley husk (obtained from the spent grains in the brewing process) is reported. With the proposed process the three main components of the lignocellulosic residue (cellulose, hemicellulose and lignin) are utilised. A first treatment with sulfuric acid (pre‐hydrolysis) allowed the solubilisation of hemicelluloses to give xylose and glucose‐containing liquors (suitable to make fermentation media for the continuous lactic acid (LA) production with L. pentosus) and a solid phase containing cellulose and lignin. In this set of experiments, a maximum volumetric productivity (Q_P) = 2.077 g L^?1 h^?1 and product yield (Y_P/S) = 0.62 g g^?1 were obtained for a dilution rate of 0.01 h^?1. The solid residues from pre‐hydrolysis were treated with NaOH in order to increase their cellulase digestibility, and dissolve the lignin content. The cellulose residue was used as substrates for lactic acid production by simultaneous saccharification and fermentation (SSF) in media containing Trichoderma reesei cellulases and Lactobacillus rhamnosus cells using the complete MRS broth or a cheaper medium. In both cases similar LA concentrations and volumetric productivities were achieved (P = 73.4–71.0 g L^?1 and Q_P = 1.28–1.25 g L^?1 h^?1, respectively), where P is LA concentration. The lignin solution obtained after the alkaline treatment was extracted with ethyl acetate in order to obtain the phenolic components. The extract obtained at pH 3 showed three times more antioxidant activity than the one extracted at pH 12.8, with an EC₅₀ of 1.396 g L^?1 for pH 3 and 4.604 g L^?1 for pH 12.8. The best extracts showed twice antioxidant activity than BHT. Copyright © 2007 Society of Chemical Industry     

Revalorisation of vine trimming wastes using Lactobacillus acidophilus and Debaryomyces hansenii

BACKGROUND: Mild acid treatments of vine‐shoot trimmings result in the hydrolysis of hemicellulosic sugars that can be utilised by Lactobacillus acidophilus CECT‐4179 (ATCC 832) and Debaryomyces hansenii NRRL Y‐7426 as carbon sources to obtain food additives. Since the high content of glucose in these hydrolysates reduces the effective bioconversion of xylose into xylitol by D. hansenii, the use of Lactobacillus acidophilus, one of the main probiotic species, allows this problem to be solved by the selective consumption of glucose. In order to use both sugars (glucose and xylose), hemicellulosic vine‐shoot trimming hydrolysates can be sequentially fermented by both micro‐organisms. RESULTS: It was found that, in the first step, L. acidophilus generated almost exclusively lactic acid (32.7 g of lactic acid L^?1, Q_LA = 1.363 g L^?1 h^?1, Y_LA/S = 0.72 g g^?1) by homofermentative degradation of sugars (mainly glucose), and in the second step, the remaining hemicellulosic sugars were transformed primarily into xylitol by Debaryomyces hansenii (31.3 g of xylitol L^?1, Q_Xylitol = 0.708 g L^?1 h^?1, Y_Xylitol/S = 0.66 g g^?1). Furthermore, L. acidophilus proved to be a strong cell‐bounded biosurfactant producer. Cell extracts were able to reduce the surface tension (ST) of PBS in 18 mN m^?1 units. Lactobacillus acidophilus cells showed no difference in viability before or after PBS extraction of biosurfactants, achieving values of 0.9 × 10⁹ colony‐forming units (CFU) mL^?1 in both cases. CONCLUSIONS: These results have made a serious contribution to the re‐evaluation of a useless and pollutant residue, producing a wide range of natural food additives. Copyright © 2008 Society of Chemical Industry     

Xylitol bioproduction from wheat straw: hemicellulose hydrolysis and hydrolyzate fermentation

A 2² central composite design with five center points was performed to estimate the effects of temperature (120, 130 and 140 °C) and acid loading (100, 150 and 200 mg g^?1) on the yield of monomeric xylose recovery from wheat straw hemicellulose (Y_S/RM). Under the best hydrolysis condition (140 °C and 200 mg g^?1), a Y_S/RM of 0.26 g g^?1 was achieved. After vacuum concentration and detoxification by pH alteration and active charcoal adsorption, the hydrolyzate was used as source of xylose for xylitol bioproduction in a stirred tank reactor. A xylitol production of 30.8 g L^?1 was achieved after 54 h^?1 of fermentation, resulting in a productivity (Q_P) of 0.57 g L^?1 h^?1 and bioconversion yield (Y_P/S) of 0.88 g g^?1. The maximum specific rates of xylose consumption and xylitol production were 0.19 and 0.15 g g^?1 h^?1, respectively. Copyright © 2006 Society of Chemical Industry     

Comparative evaluation of laboratory-scale silages using standard glass jar silages or vacuum-packed model silages

BACKGROUND: The objective of this study was to compare the fermentation variables of laboratory‐scale silages made in glass preserving jars (GLASS) and vacuum‐packed plastic bags (Rostock model silages, ROMOS). Silages were prepared from perennial ryegrass (fresh and wilted, 151 g kg^?1 and 286 g kg^?1 dry matter (DM), respectively) and remoistened coarsely ground rye grain (650 g kg^?1 DM) either with or without the addition of a lactic acid bacteria inoculant (3 × 10⁵ colony forming units (cfu) g^?1, LAB). Quintuplicate silos were opened on days 2, 4, 8, 49 and 90. RESULTS: Silage pH (P = 0.073), acetic acid content (P = 0.608) and ethanol content (P = 0.223) were not influenced by the ensiling method. The contents of DM (P < 0.001) and propionic acid (P = 0.008) were affected by the ensiling method, but mean differences were only marginal. In ROMOS the concentration of lactic acid was increased (P = 0.007) whereas butyric acid was produced less (P = 0.001) when compared to GLASS. This suggested slightly better ensiling conditions for ROMOS. CONCLUSIONS: ROMOS represents a reasonable alternative to glass jar silages and opens the possibility for further investigations, e.g. studying the impact of packing density as well as the quantitative and qualitative analysis of fermentation gases. Copyright © 2010 Society of Chemical Industry     

Production of detoxified sorghum straw hydrolysates for fermentative purposes

Sorghum straw can be hydrolysed to obtain monosaccharide solutions, mainly containing xylose. The usual biotechnological application of xylose is its bioconversion to xylitol. The global process from straw to xylitol can give an added value to the sorghum straw. The process has the following sequential steps: reduction of size, acid hydrolysis, neutralization, detoxification, fermentation, recovery and purification. This work deals with the optimization of the detoxification process of sorghum straw hydrolysates with activated charcoal. The variables evaluated were pH (1–5), contact time (20–60 min) and activated charcoal charge (20–33 g kg^?1). Mathematical models were obtained through a factorial experimental design. The models suggest that optimal conditions for detoxification are pH 1, contact time of 29 min and a charcoal charge of 33 g kg^?1. These conditions allowed hydrolysates with 54.2 g xylose L^?1, 13.5 g glucose L^?1, 12 g arabinose L^?1, 0.2 g furfural L^?1 and 0.0 g acetic acid L^?1 to be obtained. The results suggest that performing the detoxification step before the neutralization step gave the best outcome. Fermentations by Candida parapsilosis NRRL Y‐2315 were performed and it was confirmed that the treated hydrolysate is suitable for xylitol production, yielding up to 17 g L^?1 of this polyol. Copyright © 2006 Society of Chemical Industry     

Acid hydrolysis and fermentation of brewer's spent grain to produce xylitol

The hemicellulosic fraction of brewer's spent grain (BSG) was hydrolysed with diluted acid under different conditions of liquid/solid ratio (8–12 g g⁻¹), sulfuric acid concentration (100–140 mg g⁻¹ dry matter) and reaction time (17–37 min) in order to produce a liquor with a large amount of xylose and good fermentability to produce xylitol. Results showed that all the evaluated reaction conditions were able to hydrolyse xylan and arabinan with efficiencies higher than 85.8 and 95.7% respectively, and even under the mildest reaction condition a considerable amount (92.7%) of the hemicellulosic fraction could be extracted. The hydrolysates presented different fermentabilities when used as fermentation media for xylitol production by Candida guilliermondii yeast, owing to the differences in their composition. Based on statistical analysis, the best condition for BSG acid hydrolysis was the use of a liquid/solid ratio of 8 g g⁻¹, 100 mg H₂SO₄ g⁻¹ dry matter and a reaction time of 17 min. Under this condition a high extraction efficiency of hemicellulosic sugars (92.7%) and good fermentation results (Y_P/S = 0.70 g g⁻¹ and Q_P = 0.45 g dm⁻³ h⁻¹) were attained. Copyright © 2005 Society of Chemical Industry     

Effect of calcium chloride on mechanical properties and microbiological characteristics of cv. Conservolea naturally black olives fermented at different sodium chloride levels

The effect of calcium chloride (CaCl₂)(5 gL^?1) and sodium chloride (NaCl) concentration (40, 60 and 8 gL^?1) on the microbiological and mechanical properties of naturally black olives of cv. Conservolea in brines was studied. In 40 and 60 g L^?1 brines the growth of lactic acid bacteria was favoured over that of yeasts, resulting in rather complete lactic acid fermentation as indicated by high free acidity (9.8–11.5 g lactic acid L^?1) and low pH (3.7–3.8). At 80 g L^?1 brine, yeasts were the dominant members of the microflora, rendering a product with lower acidity (8 g lactic acid L^?1) and higher pH (4.3–4.5). In the presence of CaCl₂ there was a consistent increase in the depth of the peripheral region in which cell wall breakage occurred. When cells separated, perforated walls were observed at sites associated with plasmodesmata. The flesh was strongest and stiffest when CaCl₂ was added to olives treated with 40 g L^?1 brine, consistent with cell wall breakage being the predominant mode of failure. The only observed effect on the mechanical properties of the skin was a stiffening at 60 g L^?1 brine on addition of CaCl₂. Copyright © 2007 Society of Chemical Industry     

The effects of the rate of addition of formic acid and sulphuric acid on the ensilage of perennial ryegrass in laboratory silos

Perennial ryegrass was ensiled in laboratory silos after addition of formic acid (850 g kg^?1) or sulphuric acid (906 g kg^?1) at rates of 0, 2, 4 and 6 litres t^?1 fresh grass. Silos were opened after 6, 18 and 90 days and the silage subjected to chemical and microbiological analysis. The untreated control was poorly fermented with a final pH of 4.7, a butyric acid concentration of 19 g kg^?1 dry matter (DM) and an NH₃-N content of 275 g kg^?1 total nitrogen (TN). For the formic acid treatments the 2 litre t^?1 and 6 litre t^?1 levels both produced well-preserved silages but they were of different types. The silage treated with 2 litre t^?1 had a pH of 4.0, a lactic acid concentration of 92 g kg^?1 DM and 161 g NH₃-N kg^?1 TN, whereas with the 6 litre t^?1 treatment, fermentation had been severely restricted. The pH was 4.2, the lactic acid concentration was only 8 g kg^?1 DM and the NH₃-N content was 80 g kg^?1 TN. However, formic acid at 4 litre t^?1 produced a badly fermented silage of final pH 5.0 with lactic acid and butyric acid concentrations of 16 and 15 g kg^?1 DM, respectively, and an NH₃-N content of 149 g kg^?1 TN. Sulphuric acid at 2 and 4 litres t^?1 produced silages of low lactic acid contents, 36 and 24 g kg^?1 DM, and they also contained butyric acid in concentrations of 13 and 11 g kg^?1 DM; respective NH₃-N contents were 206 and 114 g kg^?1 DM. When sulphuric acid was added at 6 litres t^?1, despite a reduction in the pH of the grass to 3.5, fermentation was not restricted as it was with the equivalent level of formic acid. Lactic acid was present at 27 g kg^?1 DM and the ethanol concentration was very high at 66 g kg^?1 DM; the sulphuric acid-treated silages were characterised by high yeast counts. At the higher rates of addition, formic acid reduced the.     

Variation in short chain fatty acid and ethanol concentration resulting from the natural fermentation of wheat and barley for inclusion in liquid diets for pigs

Fifty‐six samples of wheat and 44 samples of barley were taken, at harvest, from locations across the UK. Lactic acid bacteria (LAB) and yeasts were enumerated before the samples were ground. Following grinding, triplicate 30‐g samples of each cereal were mixed with sterile distilled water and incubated at 30, 35 or 40 °C. Samples were taken immediately after mixing and at 24‐h intervals for analysis of short‐chain fatty acids (SCFA) and ethanol by isocratic ion‐exclusion liquid chromatography. The number of LAB and yeasts present in samples ranged from 0 to 5.0 (mean 2.25 ± 1.31) and 3.30 to 6.25 (mean 4.96 ± 0.74) log₁₀ colony‐forming units (cfu) ml^?1 respectively. At 30 °C the mean concentrations (mmol l^?1) of SCFAs and ethanol were, lactic acid 59.6 ± 40.0 (range 0.14–134.9), acetic acid 23.2 ± 11.1 (range 2.9–51.4), butyric acid 17.2 ± 16.8 (range 0.0–62.2) and ethanol 15.0 ± 9.0 (range 4.6–53.7) respectively. After fermentation for 24 h only 9 of 300 fermentations produced more than 75 mmol l^?1 lactic acid, which has previously been demonstrated to prevent the growth of Salmonella in liquid pig feed. Fermenting at 35 or 40 °C had no effect on lactic acid concentration but significantly (p < 0.001) increased the concentrations of acetic and butyric acids and ethanol. These results indicate that natural fermentation cannot be relied upon to produce levels of SCFAs that will prevent the proliferation of enteropathogens. Copyright © 2004 Society of Chemical Industry     

Selection of lactic acid bacteria for acidification of brown juice (grass juice), with the aim of making a durable substrate for L‐lysine fermentation

BACKGROUND: Brown juice is a waste product from the green crop‐drying industry. Heating and pressing of green crops prior to drying produces a juice rich in nutrients, which can be converted to a stable universal fermentation medium by lowering its pH to 4.0–4.5 via lactic acid fermentation. The aim of this study was to select a strain of lactic acid bacteria for industrial acidification of brown juice. RESULTS: Several strains were tested in fermentation experiments and Lactobacillus salivarius ssp. salivarius DSM 20555 was found to be the best choice. It showed high growth rates at temperatures ranging from 40 to 48 °C, with an optimum temperature of 46 °C (µ_max = 2.2 h^?1), and maintained a high productivity at pH 4.0 in continuous fermentation. The highest productivity of 7.23 g L^?1 h^?1 was found at a dilution rate of 1.0 h^?1. CONCLUSION: With today's increased focus on utilisation of residues from food and agro‐industry, coupled with restrictions on their use as fertiliser for farmlands, lactic acid fermentation could play a significant role in conservation of these nutrient‐rich liquids. This study shows that Lb. salivarius ssp. salivarius DSM 20555 is a very promising micro‐organism for use in such a process. Copyright © 2008 Society of Chemical Industry     

Improvement of L(+)‐lactic acid production from cassava wastewater by Lactobacillus rhamnosus B 103

BACKGROUND: L (+)‐Lactic acid is used in the pharmaceutical, textile and food industries as well as in the synthesis of biodegradable plastics. The aim of this study was to investigate the effects of different medium components added in cassava wastewater for the production of L (+)‐lactic acid by Lactobacillus rhamnosus B 103. RESULTS: The use of cassava wastewater (50 g L^?1 of reducing sugar) with Tween 80 and corn steep liquor, at concentrations (v/v) of 1.27 mL L^?1 and 65.4 mL L^?1 respectively led to a lactic acid concentration of 41.65 g L^?1 after 48 h of fermentation. The maximum lactic acid concentration produced in the reactor after 36 h of fermentation was 39.00 g L^?1 using the same medium, but the pH was controlled by addition of 10 mol L^?1 NaOH. CONCLUSION: The use of cassava wastewater for cultivation of L. rhamnosus is feasible, with a considerable production of lactic acid. Furthermore, it is an innovative proposal, as no references were found in the scientific literature on the use of this substrate for lactic acid production. Copyright © 2010 Society of Chemical Industry     

Malolactic fermentation in sea buckthorn (Hippophaë rhamnoides L.) juice processing

Malolactic fermentation (MLF) traditionally used in winemaking was applied to sea buckthorn to reduce the high sourness of the berry juice. Chemical and microbiological aspects, as well as sensory properties of the juice during MLF were studied in order to develop an optimal process. In 1:1 water diluted juice with malic acid content of 15 g/l and pH 2.8, efficient conversion of l-malic acid to l-lactic acid was achieved with direct inoculation of unadapted Oenococcus oeni at a cell density of 10⁹ CFU/ml. The rapid malic acid degradation was performed by non-growing bacterial cells without loss of sugars, vitamin C, or pulp oil. More than 50% of the initial malic acid was metabolized to lactic acid and CO₂ already in 12 h of fermentation and a significant decrease in sourness and astringency was noticed. In 24 h fermentation, pH value was increased to 3.1 and only 3 g/l malic acid remained in the juice. Prolonged fermentation had only minor effect on malolactic reaction, but off-flavor of the juice began to increase.     

In vitro evaluation of the fermentation of added‐value agroindustrial by‐products: cactus pear (Opuntia ficus‐indica L.) peel and pineapple (Ananas comosus) peel as functional ingredients

Agroindustrial by‐products derived from fruit processing are an important source of biocompounds that can be used as functional food ingredients. The objective of this work was to evaluate cactus pear and pineapple peel flours as an alternative carbon source during fermentation using bacteria with probiotic potential. The total fibre content of both flours was over 60%, with total soluble carbohydrate content around 20%, indicating a good carbon source for lactic acid bacteria. Kinetic parameters indicate that peel flours are a suitable carbon source because the lactic acid bacteria grow (mean growth rate constant, k, values close to glucose, 1.52 h) and acidify the culture media (maximum acidification rate, V_max, approximately 1.60 pH × 10^?3 min^?1). There was no difference in prebiotic potential or prebiotic activity score for both the peel flours. Pediococcus pentosaceus performs better during fermentation. In this respect, cactus pear and pineapple peel flours can be used as functional ingredients due to their fermentable properties.     

Aflatoxins and cyclopiazonic acid in feed and milk from dairy farms in São Paulo,Brazil

The occurrence of aflatoxins (AF) B₁, B₂, G₁, G₂ and cyclopiazonic acid (CPA) in feeds, and AFM₁ and CPA in milk was determined in dairy farms located in the northeastern region of São Paulo state, Brazil, between October 2005 and February 2006. AF and CPA determinations were performed by HPLC. AFB₁ was found in 42% of feed at levels of 1.0–26.4 µg kg^?1 (mean: 7.1 ± 7.2 µg kg^?1). The concentrations of AFM₁ in raw milk varied between 0.010 and 0.645 µg l^?1 (mean: 0.104 ± 0.138 µg l^?1). Only one sample was above the tolerance limit adopted in Brazil (0.50 µg l^?1) for AFM₁ in milk. Regarding CPA in feed, six (12%) samples showed concentrations of 12.5–153.3 µg kg^?1 (mean: 57.6 ± 48.7 µg kg^?1). CPA was detected in only three milk samples (6%) at levels of 6.4, 8.8 and 9.1 µg l^?1. Concentrations of aflatoxins and CPA in feed and milk were relatively low, although the high frequency of both mycotoxins indicates the necessity to continuously monitor dairy farms to prevent contamination of feed ingredients.     

Optimisation of fermentation conditions for probiotication of sorghum wort by Lactobacillus acidophilus LA5

Probiotics are considered as significant segments of functional foods. The response surface methodology was used to optimise the fermentation process conditions for the development of a probiotic sorghum wort beverage fermented with Lb. acidophilus LA5. The central composite design was applied with three fermentation parameters such as temperature, inoculation dosage and initial pH. Each parameter was varied at three levels. All parameters had single or interaction significant effects (P < 0.05) on the response variables. The models were highly significant with very low P ‐values. The optimum fermentation conditions were as follows: temperature 33 °C, inoculation dosage 0.8 OD₆₀₀ and pH 5.3. Under these conditions, a probiotic beverage with viable bacterial cell concentration of 8.0 log10 cfu mL^?1, final pH 3.7, lactic acid 3.2 g L^?1 and total sugar 52.7 g L^?1 can be produced. The validation experiments showed a good agreement between the experimental and predicted values. The results showed that sorghum wort is a suitable medium to produce probiotic beverages fermented with Lb. acidophilus LA5.     

Production of a Lactobacillus plantarum starter with linamarase and amylase activities for cassava fermentation

Lactobacillus plantarum strain A6 isolated from cassava, cultured on cellobiose MRS medium showed a growth rate of 0.41 h^?1, a biomass yield of 0.22 g g^?1, and produced simultaneously an intracellular linamarase (76.4 U g^?1 of biomass) and an extracellular amylase (36 U ml^?1). The synthesis of both enzymes was repressed by glucose. The use of such a strain as a cassava fermentation starter for gari production had the following influences: a change from a hetero-fermentative pattern observed in natural fermentation to a homofermentation, a lower final pH, a faster pH decline rate and a greater production of lactic acid (50 g kg^?1 DM). However, this starter did not appear to play a significant role in cassava detoxification, since it was observed that the level of endogenous linamarase released during the grating of the roots was sufficient to permit the complete and rapid breakdown of linamarin.     

Improving downstream processes to recover tartaric acid,tartrate and nutrients from vinasses and formulation of inexpensive fermentative broths for xylitol production

BACKGROUND: Vinasses, the main liquid wastes from the distillation process of grape marc and wine lees, are acidic effluents with high organic content, including acids, carbohydrates, phenols, and unsaturated compounds with high chemical oxygen demand, biological oxygen demand and solid concentrations. These wastes can be revalued to provide additional benefits when they are employed as feedstock of some compounds including tartaric acid, calcium tartrate and economic nutrients for the elaboration of fermentable broths. RESULT: This study attempts to recover tartaric acid and calcium tartrate from vinasses. All the tartaric acid initially solubilised was recovered in both processes. The residual streams can be successfully employed as economic nutrients for the xylose to xylitol bioconversion, achieving higher global volumetric productivities (Q_{P, xylitol} = 0.232 g L^?1 h^?1) and products yields (Y_xylitol/S = 0.57 g g^?1) than fermentations carried out using commercial nutrients (Q_{P, xylitol} = 0.193 g L^?1 h^?1 and Y_xylitol/S = 0.55 g g^?1 respectively). CONCLUSION: Tartaric acid can be recovered from vinasses in the form of tartaric acid crystals and calcium tartrate. The residual streams generated in the process can be used as economic nutrients for the production of xylitol by D. hansenii. Copyright © 2010 Society of Chemical Industry