Cyanide detoxification in cassava for food and feed uses

Cassava (Manihot esculenta Crantz) is an important tropical root crop providing energy to about 500 million people. The presence of the two cyanogenic glycosides, linamarin and lotaustralin, in cassava is a major factor limiting its use as food or feed. Traditional processing techniques practiced in cassava production are known to reduce cyanide in tubers and leaves. Drying is the most ubiquitous processing operation in many tropical countries. Sun drying eliminates more cyanide than oven drying because of the prolonged contact time between linamarase and the glucosides in sun drying. Soaking followed by boiling is better than soaking or boiling alone in removing cyanide. Traditional African food products such as gari and fufu are made by a series of operations such as grating, dewatering, fermenting, and roasting. During the various stages of gari manufacture, 80 to 95% cyanide loss occurs. The best processing method for the use of cassava leaves as human food is pounding the leaves and cooking the mash in water. Fermentation, boiling, and ensiling are efficient techniques for removing cyanide from cassava peels.

Cyanide degradation by Rhizopus oryzae

Rhizopus oryzae, a mucoraceous fungus associated with the postharvest spoilage of cassava was found to effectively metabolize cyanide. Degradation of cyanogenic glycosides of cassava by R. oryzae was studied by growing the organism in potato dextrose broth with and without linamarin and potassium cyanide. The influence of adaptation of the organism to low and high cyanide concentrations on both growth and the release of extracellular rhodanese into cyanide-containing media was studied. Nonadapted cultures of R. oryzae grow poorly when compared with the cyanide-adapted cultures. However non-adapted R. oryzae cultures released large quantities of rhodanese when compared with the adapted ones. Potassium cyanide (1.0 mM) was found to be an efficient inducer of rhodanese whereas potassium cyanide (5.0 mM) repressed the release of rhodanese. A significant inductive effect was produced by thiosulphate and thiocyanate. Linamarin repressed the rhodanese activity of cultures during the growth phase. Rhizopus oryzae also elaborated extracellular linamarase during its growth in broth with and without linamarin. This study revealed the potential use of R. oryzae in detoxifying the cyanogenic glycosides in cassava feed and food preparations as well as in the effective disposal of cyanide in industrial wastes.

Comparison of ethanol yield from pretreated lignocellulo-starch biomass under fed-batch SHF or SSF modes

The ethanol yields from lignocellulo-starch biomass (peels of sweet potato, elephant foot yam, tannia, greater yam and beet root) by fed-batch separate hydrolysis and fermentation (F-SHF) and simultaneous saccharification and fermentation (F-SSF) using Saccharomyces cerevisiae were compared. Fed-batch saccharification of steam or dilute sulphuric acid pretreated biomass enhanced the reducing sugar yield which resulted in high RS consumption, volumetric ethanol productivity and ethanol yield during the first 24 h fermentation under F-SHF mode, while continuous production and utilization of reducing sugars occurred up to 72 h in F-SSF. Dilute sulphuric acid pretreated residues under F-SHF gave higher ethanol yield (34-43 g/L) and productivity (274-346 ml/kg dry biomass) than steam pretreatment (27-36 g/L and 223-295 ml/kg respectively), while F-SSF was superior for steam pretreated peels of sweet potato, elephant foot yam and tannia giving ethanol yields from 281 to 302 ml/kg. Glucose and xylose were present in all the hydrolysates with a preponderance of glucose and fermentation resulted in significant reduction in glucose levels in both F-SHF and F-SSF. Higher levels of total soluble phenolics and hydroxymethyl furfural were observed in the hydrolysates from dilute sulphuric acid pretreatment and yeast assimilated/detoxified part of the inhibitors, while only trivial amounts of furfural were present due to the low xylose content in the hydrolysates. Continuous formation led to higher accumulation of inhibitors in F-SSF despite supplementation with the detoxification mix comprising Tween 20, polyethylene glycol and sodium borohydride. F-SHF of dilute sulphuric acid pretreated biomass could be considered as a comparatively advantageous process where only one time feeding of enzyme cocktail and yeast was adopted compared to multiple feeds of enzymes and yeast along with other additives such as detoxification mix or nutrient solution in F-SSF.

Gluten-free starch noodles from sweet potato with reduced starch digestibility and enhanced protein content

Sweet potato starch (SPS) noodles despite being gluten-free, has low nutritional value as it lacks proteins, minerals, vitamins etc. The objective of this study was to develop gluten-free starch noodles from sweet potato with enhanced protein content through fortification with whey protein concentrate (WPC) and to study the effect of protein fortification and blending SPS with banana (BS), cassava (CS) and mung bean (MBS) starches and annealed cassava starch (ACS) in reducing the starch digestibility. The highest protein retention in cooked noodles was obtained for 20 % WPC fortification, while the lowest starch digestibility was observed for 40 % BS fortified noodles followed by 50 % ACS fortified noodles. The highest resistant starch (RS) retention was for BS and ACS fortified noodles, which also had medium glycemic index of 66.3 (BS) and 67.2 (ACS). High sensory scores were obtained for the BS and 20 % WPC fortified noodles. The study showed that protein and/or BS fortification with SPS could enhance the acceptability as well as functional value of SPS noodles.

Bioethanol production from microwave-assisted acid or alkali-pretreated agricultural residues of cassava using separate hydrolysis and fermentation (SHF)

The effect of microwave (MW)-assisted acid or alkali pretreatment (300 W, 7 min) followed by saccharification with a triple enzyme cocktail (Cellic, Optimash BG and Stargen) with or without detoxification mix on ethanol production from three cassava residues (stems, leaves and peels) by Saccharomyces cerevisiae was investigated. Significantly higher fermentable sugar yields (54.58, 47.39 and 64.06 g/L from stems, leaves and peels, respectively) were obtained after 120 h saccharification from MW-assisted alkali-pretreated systems supplemented (D+) with detoxification chemicals (Tween 20 + polyethylene glycol 4000 + sodium borohydride) compared to the non-supplemented (D0) or MW-assisted acid-pretreated systems. The percentage utilization of reducing sugars during fermentation (48 h) was also the highest (91.02, 87.16 and 89.71%, respectively, for stems, leaves and peels) for the MW-assisted alkali-pretreated (D+) systems. HPLC sugar profile indicated that glucose was the predominant monosaccharide in the hydrolysates from this system. Highest ethanol yields (Y_E, g/g), fermentation efficiency (%) and volumetric ethanol productivity (g/L/h) of 0.401, 78.49 and 0.449 (stems), 0.397, 77.71 and 0.341 (leaves) and 0.433, 84.65 and 0.518 (peels) were also obtained for this system. The highest ethanol yields (ml/kg dry biomass) of ca. 263, 200 and 303, respectively, for stems, leaves and peels from the MW-assisted alkali pretreatment (D+) indicated that this was the most effective pretreatment for cassava residues.

Alpha-amylase inhibitor changes during processing of sweet potato and taro tubers

Alpha-amylase inhibitor changes during processing of sweet potatoes (Ipomoea batatas) and taro (Colocasia esculenta) indicated that varietal differences profoundly influence the thermal inactivation profile. The alpha-amylase inhibitors of taro were almost totally inactivated during oven drying of the chips at 90 degrees C and 100 degrees C for 24 h, while 0.8-10% activity was retained in sweet potato chips under the same conditions. Relatively better thermal stability was exhibited by the sweet potato amylase inhibitors at lower temperatures (70 and 80 degrees C) as well. Cooking by boiling the tuber pieces in water resulted in retention of 29-59% amylase inhibitor in sweet potato and 11-16% in taro. Microwave baking was a better method for inactivation of amylase inhibitors in these tubers. Flour prepared from the tubers retained only trivial amounts of the inhibitor.

Inactivation of trypsin inhibitors in sweet potato and taro tubers during processing

In order to understand the extent of elimination of trypsin inhibitors during processing of sweet potato (Ipomoea batatas) and taro (Colocasia esculenta) tubers, a detailed study was conducted using tubers processed by oven drying, cooking, and microwave baking. Between 80 and 90% trypsin inhibitor (TI) activity was retained in sweet potato chips up to 2h at 70 degrees C. Among the four cultivars of sweet potatoes, RS-III-2 trypsin inhibitors were more heat labile. Heating at 100 degrees C led to rapid inactivation of TI of sweet potatoes. Varietal differences in thermal stability were more pronounced for the trypsin inhibitors of taro than sweet potatoes. Taro inhibitors were also more rapidly inactivated than sweet potato TI. Between 17 and 31% TI activity was retained in cooked tuber pieces of sweet potatoes, while only 3-10% were retained in taro cultivars. Very effective inactivation of trypsin inhibitors of sweet potatoes and taro could be obtained through microwave baking. Flour prepared from taro was devoid of TI activity, while 5-12% TI activity was retained in the flour prepared from sweet potatoes. The study clearly established that among the four techniques used, microwave baking and flour preparation were the best methods to eliminate TI from sweet potatoes and taro.

Production of high fructose syrup from cassava and sweet potato flours and their blends with cereal flours

Despite being a rich source of starch, root crops such as cassava and sweet potato have not been widely exploited for the production of high fructose syrup (HFS), which is a highly valued sweetener for the food and beverage industries. The major factors contributing to the cost of production of HFS are the cost and labor-intensive steps in the production of starch, different processing temperatures and pH for the enzyme reactions, poor extractability of starch, etc. With the objective of overcoming the cost associated with the preparation of starch, the feasibility of using native cassava/sweet potato flours and their blends with rice flour and wheat flour, as the raw material for HFS production was investigated. The saccharified slurry from cassava--rice flour blends contained 70-72 g reducing sugars/100 g, which was higher than that released from native cassava flour (~69%). Blends of sweet potato with rice or wheat yielded saccharified mash with lower content of reducing sugars (60-66%). Although the percentage conversion to fructose after isomerization was similar for cassava/sweet potato or their blends with cereal flours (42-43%), fructose yield was higher in native cassava flour and cassava-rice blends (28-29 g/100 g) than the other flour blends.

Strategies for enzyme saving during saccharification of pretreated lignocellulo-starch biomass: effect of enzyme dosage and detoxification chemicals

Two strategies leading to enzyme saving during saccharification of pretreated lignocellulo-starch biomass (LCSB) was investigated which included reducing enzyme dosage by varying their levels in enzyme cocktails and enhancing the fermentable sugar yield in enzyme-reduced systems using detoxification chemicals. Time course release of reducing sugars (RS) during 24-120 h was significantly higher when an enzyme cocktail containing full dose of cellulase (16 FPU/g cellulose) along with half dose each of xylanase (1.5 mg protein/g hemicelluloses) and Stargen (12.5 μl/g biomass) was used to saccharify conventional dilute sulphuric acid (DSA) pretreated biomass compared to a parallel system where only one-fourth the dose of the latter two enzymes was used. The reduction in RS content in the 120 h saccharified mash to the extent of 3-4 g/L compared to the system saccharified with full complement of the three enzymes could be overcome considerably by supplementing the system (half dose of two enzymes) with detoxification chemical mix incorporating Tween 20, PEG 4000 and sodium borohydride. Microwave (MW)-assisted DSA pretreated biomass on saccharification with enzyme cocktail having full dose of cellulase and half dose of Stargen along with detoxification chemicals gave significantly higher RS yield than DSA pretreated system saccharified using three enzymes. The study showed that xylanase could be eliminated during saccharification of MW-assisted DSA pretreated biomass without affecting RS yield when detoxification chemicals were also supplemented. The Saccharification Efficiency and Overall Conversion Efficiency were also high for the MW-assisted DSA pretreated biomass. Since whole slurry saccharifcation of pretreated biomass is essential to conserve fermentable sugars in LCSB saccharification, detoxification of soluble inhibitors is equally important as channelling out of insoluble lignin remaining in the residue. As one of the major factors contributing to the cost of ethanol production from LCSB is the cost of enzymes, appropriate modification of enzyme cocktail based on the composition of the pretreated biomass coupled with effective detoxification of the slurry would be a promising approach towards cost reduction.

Impact of family support on psychiatric disorders and seizure control in patients with juvenile myoclonic epilepsy

OBJECTIVE

Psychiatric disorders (PDs) are frequently observed in patients with juvenile myoclonic epilepsy (JME). In this study, we aimed to assess factors associated with PDs in patients with JME.

METHODS

Retrospective analysis of data of 90 consecutive patients with JME was performed. Assessment of DSM-IV Axis I clinical disorders was done using Structured Clinical Interview for Axis I. Diagnosis of PDs is made when the score exceeds the threshold provided by the DSM-IV. We also applied the Global Assessment of Functioning (GAF) scale which is part of the multiaxial evaluation of the DSM-IV (Axis-V). Using seizure frequency score at presentation, we classified subjects into controlled and uncontrolled groups.

RESULTS

In the current cohort, 29 (32.2%) patients were diagnosed with PDs. Fewer patients with PDs had family support (48.3% vs. 83.6%; p=0.001). Lifetime prevalence of PDs was higher among patients with current PDs (96.6% vs. 18.0%; p<0.0001). Subthreshold illness was not different between the groups (17.2% vs. 27.9%; p=0.204). Mean GAF was higher in patients without PDs than in patients with PDs (89.19±6.92 vs. 64.22±9.76; p<0.0001). Patients with PDs had lower seizure control (7.8% vs. 73.1%; p<0.0001) compared with patients without PDs. Logistic regression analysis for factors associated with diagnosis of PDs revealed that none of the factors significantly affected the odds of seizure control. Patients with lack of family support had poor seizure control (0% vs. 36.9%; p<0.0001); 51.7% of patients with JME with PDs reported lack of family support. Patients with family support had lower lifetime prevalence of PDs (30.8% vs. 76.0%; p<0.0001), whereas patients with JME without family support had lower levels of education (8.0% vs. 35.4%; p=0.009).

CONCLUSION

Lack of family support is associated with poor seizure control and higher incidence of PDs in patients with JME. Lack of family support increases neither the odds of PDs nor seizure control.