Effects of pH and dissolved oxygen on the synthesis of γ‐glutamyltranspeptidase from Bacillus subtilis SK 11.004

BACKGROUND: γ‐Glutamyltranspeptidase (GGT; EC 2.3.2.2) is a widely distributed enzyme that is of interest in the food industry. In this study the effects of pH and dissolved oxygen (DO) on GGT synthesis from Bacillus subtilis SK 11.004 were investigated. RESULTS: GGT production increased to 0.5 U mL^?1 when the pH value was controlled at 6.5. The control of a single DO level revealed that the highest specific growth rate (3.42 h^?1) and GGT production rate (0.40 U g^?1 mL^?1) were obtained at DO levels of 40 and 10% respectively. To satisfy the different oxygen demands at different stages of cell growth and GGT synthesis, a stage DO level control strategy was designed as follows: 40% from 0 to 4 h, 30% from 4 to 6 h and 10% from 6 to 18 h. Furthermore, the maximum biomass (2.27 g L^?1) and GGT production (3.05 U mL^?1) could be obtained using a fermentation strategy combining a constant pH value with stage DO level control. CONCLUSION: The proposed fermentation strategy resulted in a 13.7‐fold increase in GGT production. This finding should be of great importance for the industrial production of GGT. Copyright © 2011 Society of Chemical Industry     

Continuous baker's yeast production using orange peel as promoting support in the bioreactor

Improvements in maximum growth rate and productivity in biomass production using orange peel as promoter were observed in batch aerobic fermentation. Daily biomass productivity and biomass yield up to 14.9 g (dry weight) L^?1 and 0.22 g (dry weight) g^?1 utilized sugar respectively in batch aerobic fermentation by the presence of orange peel as promoter were reported. A novel bioreactor for continuous aerobic fermentation of molasses is described and its suitability for baker's yeast production using orange peel as promoter is investigated. The continuous bioreactor was operated for 12 days, stored for 20 days at 10 °C and operated again for another 13 days without any diminution of biomass productivity. Daily biomass productivity, yield and conversion up to 11.2 g (dry weight) L^?1, 0.16 g (dry weight) produced g^?1 utilized sugar and 90.4% respectively were recorded. The possibility of using such a system for industrial continuous baker's yeast production is discussed. Copyright © 2005 Society of Chemical Industry     

Standardisation of the sour cassava starch reduces the processing time by fermentation water monitoring

This work investigated the pH, titratable acidity and total solids of the cassava starch fermentation water, using the traditional method and a method modified through the addition of glucose. Sour cassava starch production controlled by the characteristic of the fermentation water produced the best product (biscuit specific volume of 7.66 ± 0.41 mL g^?1) at 33th day of fermentation in the modified method and at 85th day (biscuit specific volume of 6.53 ± 0.59 mL g^?1) in traditional method. But, comparatively to the commercial sour cassava starch (biscuit specific volume of 3.48 ± 0.12 mL g^?1), both traditional and modified methods, controlled by titratable acidity of fermentation water, can be retired from the fermentation tank in the 19th and 32th day of fermentation, with biscuit specific volume of 4.75 ± 0.30 and 5.17 ± 0.46 mL g^?1, respectively. Determining fermentation time can help to standardise sour cassava starch and to promote future applications of the fermentation water as a raw material.     

Production of Beta-Carotene from Synthetic Medium by Blakeslea trispora in Fed-batch Culture

Abstract

The production of β-carotene from a synthetic medium by Blakeslea trispora in fed-batch culture was investigated. A maximum β-carotene concentration of 85.0?mg?L^?1 with productivity of 0.16?mg?L^?1?h^?1 and specific β-carotene production rate of 0.01?mg?g^?1?h^?1 was obtained by feeding the cells constantly with olive oil, cottonseed oil, soybean oil, antioxidant, and low concentration of growth factors at feeding rate of 4.2?mL?h^?1 from the beginning of the fermentation. In this case, the fed-batch culture supported high values of biomass dry weight (11.0?g?L^?1) and sugar utilization (0.976?g?g^?1). The morphology of the fungus was studied during growth in fed-batch fermentation system using an image analysis system. Zygospores are the morphological forms, which are responsible for the production of the pigment. The highest percentage of zygospores (11.44%) was correlated with the highest percentage of intracellular β-carotene (0.72%) in the total biomass dry weight. Moreover, high percentages of vacuolated hyphae, evacuated cells, and degenerated hyphae of the microorganism were observed. This was due to the formation of high amount of H₂O₂ by exposure of the microorganism to high dissolved oxygen concentration.     

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     

Production, purification and characterisation of polysaccharides from Pleurotus ostreatus with antitumour activity

BACKGROUND: Mushroom polysaccharides play an important role in functional foods because they exhibit biological modulator properties such as antitumour, antiviral and antibacterial activities. The present study involved the production, purification and characterisation of intracellular and extracellular free and protein‐bound polysaccharides from Pleurotus ostreatus and the investigation of their growth‐inhibitory effect on human carcinoma cell lines. RESULTS: Several fermentation parameters were obtained: batch polysaccharide productivities of 0.013 ± 8.12 × 10^?5 and 0.037 ± 0.0005 g L^?1 day^?1 for intracellular and extracellular polysaccharides respectively, a maximum biomass concentration of 9.35 ± 0.18 g L^?1, P_max = 0.935 ± 0.018 g L^?1 day^?1, µ_max = 0.218 ± 0.02 day^?1, Y_EP/X = 0.040 ± 0.0015 g g^?1 and Y_IP/X = 0.014 ± 0.0003 g g^?1. Some polysaccharides exhibited superoxide dismutase (SOD)‐like activity of 50‐200 units. Fourier transform infrared analysis of the polysaccharides revealed absorption bands characteristic of such biological macromolecules. Cytotoxicity assays showed that both intracellular and extracellular polysaccharides exhibited antitumour activity towards several tested human carcinoma cell lines in a dose‐dependent manner. CONCLUSION: The polysaccharides of P. ostreatus exhibited high SOD‐like activity, which strongly supports their biological effect on tumour cell lines. The extracellular polysaccharides presented the highest antitumour activity towards the RL95 carcinoma cell line and should be further investigated as an antitumour agent. Copyright © 2012 Society of Chemical Industry     

Microbiological and physicochemical properties of dry‐cured neck inoculated with probiotic of Bifidobacterium animalis ssp. lactis BB‐12

The effect of inoculum level of Bifidobacterium animalis ssp. lactis BB‐12 probiotic strain and ripening period on the quality of dry‐cured neck was studied. The microbiological parameters (Enterobacteriaceae, LAB and TVC) and physicochemical attributes (pH value, a_w, TBARS index, colour) were determined directly after fermentation at 15 °C for 3 weeks, after 6 and 12 months of ripening at 4 °C. The highest LAB count and a lower pH value were found in the meat inoculated with probiotic strain at 6.6 log cfu g^?1 (B2) followed by inoculation with probiotic strain at 6.3 log cfu g^?1 (B1). Level of inoculation had not had an influence on water activity, TBARS index and total colour parameters. Changes of fat oxidation during half‐year of ripening were limited in probiotic meat samples compared to naturally fermented control meat (C). Based on the results, it can be concluded that the most favourable physicochemical and microbiological parameters of the dry‐cured neck were obtained after 6 months of ripening. At that time, the Bifidobacterium BB‐12 at both levels is a good potential starter for meat fermentation.     

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     

Characteristics of fermentation and bioavailability of isoflavones in Korean soybean paste (doenjang) with application of Bacillus sp. KH-15

We attempted to increase the fibrinolytic activity and aglycone contents of isoflavone in doenjang prepared with Bacillus sp. KH‐15. An initial rapid increase of viable cells was observed in the first 30 days followed by a gradual decrease to 1.78 × 10⁸ CFU g^?1 wet weight. The amino type nitrogen sharply was increased after 15 days, and showed the highest level (788.7 mg%) after 90 days. The total nitrogen was increased from 2.21% to 2.52% of final content after 90 days. Soluble carbohydrate was increased to 32.9 mg g^?1 for 60 days, and after 60 days, the content was slowly decreased to 29.5 mg g^?1. A rapid increase in fibrinolytic and caseinolytic activities were observed in the first 30 and 45 days of fermentation followed by a gradual decrease to 2.54 and 144.5 U g^?1, respectively. β‐Glucosidase activity also showed a similar change pattern of the caseinolytic and fibrinoytic activities. Daidzein and genistein were increased to the maximum level of 764.5 and 561.4 mg kg^?1 at day 30, respectively. At day 90, the contents of daidzein and genistein were 661.5 and 524.9 mg kg^?1, respectively. The rats were fed a diet supplemented with either doenjang powder prepared with Bacillus sp. KH‐15 (D‐1 group) or commercial doenjang powder (D‐2 group) for 40 days. The level of serum total isoflavones in the D‐1 group was significantly higher than that in the D‐2 group.     

Production of fungal biomass from cormel process waste‐water of cocoyam (Xanthosoma sagittifolium (L) Schott) using Aspergillus oryzae obtained from cormel flour

Aspergillus oryzae obtained from spoilt cormel flour was subjected to mutation treatments using X‐rays, solar radiation and bleach. Exposure of A oryzae spores to X‐radiation of 50 kV at 20 mA s and other treatments induced both mutation and lethality in the organism. Following selection and screening of viable colonies on a medium containing cormel process waste‐water as the only carbon source, two strains, A oryzae No 15 and A oryzae No 8, which significantly (P ≤ 0.05) produced more biomass at a higher growth rate than the wild parent, were chosen for single‐cell protein production. Nutrient content of the single‐cell protein produced by the mutants was comparable to that of the wild type. Addition of 3.0 g each of (NH₄)₂SO₄, NH₄NO₃, NH₄Cl, and urea in 1 l of Xanthosoma process waste‐water increased the growth rate of mutants, with the highest increase observed with urea. Medium amended with urea also produced fungal biomass with the highest protein level of 7.97 g l^?1 for A oryzae No 8 strain compared with a protein yield of 3.97 g l^?1 obtained in the control. Total biomass produced after 54 h was 22.47 g l^?1 for A oryzae No 15 strain when urea was added, whereas only 15.20 g l^?1 was produced when no nitrogen source was added. The optimal temperature for single‐cell protein production was found to be 35 °C and the optimal pH was 3.50. A speed of 100 rpm gave the largest quantity of fungal biomass for the mutants tested. Copyright © 2003 Society of Chemical Industry     

Synthesis and in vitro digestion of resistant starch type III from enzymatically hydrolysed cassava starch

Resistant starch type III (RS III) was synthesised from cassava starch by autoclaving followed by debranching with pullulanase, at varied concentrations (0.4–12 U g^?1) and times (2–8 h), and recrystallisation (?18 to 90 °C for 1–16 h). The highest RS III yield (22 g/100 g) was obtained at an enzyme concentration of 4 U g^?1 after 8 h incubation, followed by recrystallisation at 25 °C for 16 h. Varying the recrystallisation conditions indicated that higher RS III yields (30–35 g/100 g) could be obtained at 90 °C within 2 h. Thinning cassava starch using α‐amylase prior to debranching using pullulanase did not further increase the RS III content. In vitro digestion data showed that whereas 44% RS III was digested after 6 h, the corresponding value for cassava starch was 89%.     

Batch kinetics and modelling of ethanolic fermentation of whey

The fermentation of whey by Kluyveromyces marxianus strain MTCC 1288 was studied using varying lactose concentrations at constant temperature and pH. The increase in substrate concentration up to a certain limit was accompanied by an increase in ethanol formation, for example, at a substrate concentration of 10 g L^?1, the production of ethanol was 0.618 g L^?1 whereas at 50 g L^?1 it was 3.98 g L^?1. However, an increase in lactose concentration to 100 g L^?1 led to a drastic decrease in product formation and substrate utilization. The maximum ethanol yield was obtained with an initial lactose concentration of 50 g L^?1. A method of batch kinetics was utilized to formulate a mathematical model using substrate and product inhibition constants. The model successfully simulated the batch kinetics observed at S₀ = 10 and 50 g L^?1 but failed in case of S₀ = 100 g L^?1 because of strong substrate inhibition.     

Evaluation of the conditions of carotenoids production in a synthetic medium by Sporidiobolus salmonicolor (CBS 2636) in a bioreactor

This work studied the cultivation conditions for the production of carotenoids by Sporidiobolus salmonicolor (CBS 2636) in a bioreactor. A Plackett–Burman design was used for the screening of the most important factors, followed by a complete second order design, to maximise the concentration of total carotenoids. The maximum concentration of 3425.9 μg L^?1 of total carotenoids was obtained in a medium containing 80 g L^?1 glucose, 15 g L^?1 peptone and 5 g L^?1 malt extract, with an aeration rate 1.5 vvm, 180 r.p.m., 25 °C and an initial pH of 4.0. Fermentation kinetics showed that the maximum concentration of total carotenoids was reached after 90 h of fermentation. Carotenoid bio‐production was partially associated with cell growth. The specific carotenoid production (Y_P/X) was 238 μg carotenoids/g cells, whereas Y_P/S (substrate to product yield) was 41.3 μg g^?1. The specific growth rate (μ_x) was 0.045 h^?1. The highest cell and total carotenoid productivity were 0.19 g L^?1 h^?1 and 56.9 μg L^?1 h^?1, respectively.     

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     

Proton production and consumption pathways in yeast metabolism. A chemostat culture analysis

In this investigation, a method for the accurate quantitative determination of net proton production or consumption in biological cultures has been devised. Cells are cultured under constant pH conditions. The specific rate of proton production or consumption by the culture (qH⁺, mmol h^?1 per g biomass) is proportional to the mmol of base or acid required to maintain constant pH per unit time, and this equivalence is independent of the buffering capacity of the culture medium. The above method has been applied to chemostat cultures of Candida utilis growing on glucose or glycerol as carbon source, and different nitrogen sources. The results indicate that the nitrogen assimilation pathway alone determines the value of qH⁺, and a fixed stoichiometric relationship between nitrogen uptake rate qN (meq h^?1 per g biomass) and qH⁺ has been found for each nitrogen source employed. Thus, qH⁺/qN values of +1, 0 and ? 1 were found for ammonium ions, urea and nitrate respectively. Under oxidative metabolism, the contribution of carbon catabolism to the value of qH⁺ was undetectable. Since qN may be related to growth and production of type 1 compounds in fermentation processes, the parameter qH⁺ was incorporated into a model of growth and energy metabolism in chemostat culture (Castrillo and Ugalde, Yeast 10 , 185–197, 1994), resulting in adequate simulations of experimentally observed culture performance. Thus, it is suggested that qH⁺ may be employed as a simple and effective control parameter for biotechnological processes involving biomass-related products.     

The comparison of biosorption of nutritionally significant minerals in single‐ and multi‐mineral systems by the edible microalga Spirulina sp.

BACKGROUND: This paper deals with the biosorption process as a method of enrichment of natural biomass of the edible microalga Spirulina sp. with microelement metal ions, which is of significance in terms of animal nutrition. The influence of the following process parameters was studied for the biosorption of Cr(III): pH and biomass concentration on kinetics and equilibrium of biosorption. The enrichment process were performed in single‐ and multi‐mineral systems for nutritionally significant minerals such as Cu(II), Mn(II), Co(II), Zn(II) and Cr(III) under the conditions that were determined for Cr(III). RESULTS: The best operational parameters for the process were selected as pH 5 and Cs 1 g L^?1. The maximum biosorption capacity 71.2 mg g^?1, 18.4 mg g^?1, 83.9 mg g^?1, 31. 8 mg g^?1 and 26.5 mg g^?1, were reached for Cu(II), Mn(II), Co(II), Zn(II) and Cr(III), respectively. To cover 100% of animal demand on microelements, 4.91 g of the preparation for laying hens and 9 g for swine of enriched microalgae in the single‐metal system should be added to 1 kg of fodder. In the multi‐metal system the competition between microelements was high enough to make it impossible to reach a suitable ratio between bound metal ions. CONCLUSIONS: Two methods of production of mineral feed additives were proposed: a single‐metal system and a multi‐metal system. Performing the biosorption process in the single‐metal system enabled the preparation of additives with the desired composition. Carrying out biosorption in the multi‐metal system is easier, technologically, but the ratio of bound microelements is difficult to predict. Copyright © 2009 Society of Chemical Industry     

Transforming sugars into fat – lipid biosynthesis using different sugars in Yarrowia lipolytica

In an era of ever‐increasing energy demands, a promising technology is being developed: the use of oleaginous microorganisms such as Yarrowia lipolytica to convert waste materials into biofuels. Here, we constructed two Y. lipolytica strains that displayed both increased lipid accumulation and more efficient use of biomass‐derived sugars, including glucose, fructose, galactose and inulin. The first strain, Y. lipolytica YLZ150, was derived from the French wild‐type strain W29. It had inhibited triacylglycerol mobilization (?tgl4 ) and β‐oxidation (?pox1–6 ), and it overexpressed GPD1 , DGA2 , HXK1 , the native Leloir pathway, SUC2 from Saccharomyces cerevisiae and INU1 from Kluyveromyces marxianus . The second strain, Y. lipolytica Y4779, was derived from the Polish A‐101 strain. It had inhibited β‐oxidation (?mfe2 ) and overexpressed GPD1 , DGA1 , HXK1 , YHT3, SUC2 and INU1 . In the first experiment, strain YLZ150 was batch‐cultured in media containing different hexoses; the highest values for lipid concentration and yield of lipids from the substrate were obtained using fructose (20.3 g dm^?3 and 0.14 g g^?1, respectively). In the second experiment, we grew the two strains in fed‐batch cultures to examine lipid biosynthesis from inulin (a fructose polymer). For Y4779, the lipid concentration was 10.3 g dm^?3 and the yield of lipids from substrate was 0.07 g g^?1; in contrast, for YLZ150, these values were 24 g dm^?3 and 0.16 g g^?1, respectively. The YLZ150 strain is thus able to efficiently exploit glucose, fructose, galactose, sucrose and inulin for lipid biosynthesis. Copyright © 2017 John Wiley & Sons, Ltd.     

PURIFICATION AND SOME PROPERTIES OF LINAMARASE FROM CASSAVA (Manihot esculenta) CORTEX

The enzyme linamarase (E. C. 3.2.1.21) has been purified from cassava cortex (Manihot caculenta) by techniques involving acetone precipitation, ammonium sulfate fractionation, gel filtration and ion-exchange chromatography. Two peaks of linamarase activity (A & B) were eluted by linear gradient on DEAE-Sephadex column. Both forms of the enzyme were found to catalyze similar reactions, however, at different rates. Double reciprocal plots from initial velocity data gave K_m of 1.47 mM & 1.44 mM for linamarase A & B, respectively, with linamarin as substrate. The K_m values with the artificial substrate para-nitrophenyl glucoside (PNP-G) were 0.48 mM, Both enzyme forms exhibited maximal activity at pH 6.0 and 30°C. Arrhenius plots gave activation energy (E_a) as 49 KJ/mole (11.72 Kcal mole^?1) and 36.5 KJ/mole (8.72 Kcal mole^?1) for linamarase A & B, respectively. Analysis of cyanide levels in cassava and its products with the crude enzyme showed the leaves to contain high levels of the toxic factor.     

Production of Polysaccharide by Rahnella aquatilis with Whey Feedstock

The rates were monitored on biomass increase, polysaccharide production and viscosity development of whey broth and a control synthetic broth during fermentation by Rahnella aquatilis and organic acids, lactose, peptides and free amino acids were measured. Growth curves were similar and characterized by maximum specific growth rates of 0.61 h^?1 for whey and 0.63 h^?1 for synthetic medium. The yields of polysaccharide were 0.59 g/g_lactose for the synthetic medium and 0.56 for whey. Small peptides (<4,000 Da) and most free amino acids in both fermentation media were consumed within 24h.     

Processing factors affecting the level of residual cyanohydrins in gari

Intake of cyanogens in gari, a food processed from cassava roots, is implicated in the causation of tropical ataxic neuropathy (TAN). This neurological syndrome is endemic in some communities in south‐western Nigeria. Studies have shown that methods of processing cassava roots determine the quantity of cyanogens in gari. This study was conducted to investigate the effects of the method of dewatering and the duration of fermentation on cyanogens in gari. Cassava roots (400 kg) were peeled, washed, grated and divided into 14 woven polyethylene sacks. The mash in seven of the sacks was dewatered continuously during fermentation, while the mash in the remaining seven sacks was fermented without dewatering, but dewatered at the end of fermentation. Cassava mash from each treatment was roasted into gari at 24 h intervals up to 168 h. Mean cyanohydrin content in gari roasted from cassava mash dewatered continuously during fermentation was 10.8 mg HCN eq kg^?1 dw (CI 9.7–11.9), while mean cyanohydrin content in gari roasted from cassava mash dewatered after fermentation was 6.3 mg HCN eq kg^?1 dw (CI 5.3–7.4). Mean linamarin content was 4.0 mg HCN eq kg^?1 dw (CI 3.1–4.9) and mean HCN content was 1.6 mg kg^?1 dw (CI 1.3–1.9) in gari roasted from cassava mash dewatered continuously, while mean linamarin content was 3.2 mg HCN eq kg^?1 dw (CI 2.3–4.0) and mean HCN content was 1.2 mg kg^?1 dw (CI 0.9–1.5) in gari roasted from cassava mash dewatered after fermentation. The method of dewatering cassava mash and the duration of fermentation were significantly associated with the level of cyanohydrin in gari (p < 0.001). This study shows that dewatering of cassava mash continuously during fermentation contributes to the dietary cyanide load in TAN‐affected communities. © 2002 Society of Chemical Industry