Cassava Starch Factory Research Articles

Dried cassava pulp as an alternative feedstuff for broilers: Effect on growth performance, carcass traits, digestive organs, and nutrient digestibility

Dried cassava pulp (DCP), a by-product of cassava starch factory processing, contains a large quantity of starch. Therefore, it is certainly worthwhile to investigate its use as an energy source for poultry feed. Two experiments were conducted to examine the potential use of DCP for broilers. Growth, carcass traits, length and weight of digestive organs, and nutrient digestibility were determined in broilers fed diets containing 0 to 16% DCP. Seven-day-old mixed-sex chicks (n = 240) were randomly distributed to 5 dietary treatment groups through 42 d of age (experiment 1). In experiment 2, a total of 50 chicks were randomly allotted to individual cages at 15 d and fed 1 of 5 diets for 10 d to measure digestibility. Results showed that growth performance and nutrient digestibility decreased with increasing levels of DCP. In most cases, these parameters did not change significantly when DCP was at or below 8%. A significant increase in gizzard weight and a reduction in abdominal fat were also found in broilers fed DCP. In conclusion, it is suggested that DCP be used as an energy source at inclusion levels up to 8% in broiler diets.

Optimisation of glutamic acid production from cassava starch factory residues using Brevibacterium divaricatum

There is serious concern about the disposal of solid residues left after large-scale cassava starch extraction. Storage of residues if badly managed, leads to serious environmental problems. Owing to the high starch content and organic nature of these wastes, an attempt has been made to utilise it for the production of glutamic acid, the precursor of monosodium glutamate, employing submerged fermentation using Brevibacterium divaricatum. The effect of temperature, pH, inoculum size, speed of agitation and nitrogen sources were studied. With 0.7% ammonium nitrate in the medium, highest glutamate yield of 3.86% based on the weight of the residues was obtained at 30 °C at a pH of 7.0. The highest glutamate production was recorded at 5% inoculum size at an agitation speed of 180 rpm. The study showed that the solid residues from cassava starch factories could serve as a low-cost substrate for glutamic acid production.

Transformation and Balance of Cyanogenic Compounds in the Cassava Starch Manufacturing Process

The balance of total cyanogenic compounds and distribution of each compound including bound cyanide, cyanohydrin and free cyanide were evaluated in a cassava starch factory, having a production capacity around 100 t starch per day. The production of starch began with transferring washed roots to the rasper, followed by a series of extractors, separators, dewatering centrifuge and flash dryer, with an average water consumption of 11.4 t per ton dry starch. The total amount of cyanogenic compounds entering the process varied from 28 to 43 kg HCN equivalent per day, depending on the root quality. In roots, 64% of bound cyanide was primarily found and it significantly decreased to 22% after rasping whereas the cyanohydrin content increased from 34% to 62%. Most of cyanogenic compounds, predominantly present as cyanohydrin (55 to 70%), was discharged in liquid and solid wastes, accounting for 92% and 5% of total cyanide in roots, respectively. Only a negligible amount of cyanogenic compounds remained in the starch products, having less than 2 mg HCN equivalent per kilogram dry starch. Typically, water from the separators with 91% total cyanide content was recycled to the root washer before being discharged as wastewater, whereas the liquid from the coarse extractor (43% of total cyanide) was recycled to the rasper. This could cause the accumulation of cyanogen in the process and, therefore, in the finished products. With knowledge of the balance and transformation of cyanogens in starch processing, it is possible to assure the quality of low-cyanide starch by modifying starch process features such as water circulation and pH adjustment.

Bacterial Population of a Two-Phase Anaerobic Digestion Process Treating Effluent of Cassava Starch Factory

Different groups of microorganisms in a two-phase anaerobic system were enumerated to evaluate the prevalence of specific groups and species. Total and fecal coliforms showed similar values both in acidogenic and methanogenic reactors. The fecal streptococci were 4-fold higher in the acidogenic reactor, when compared with those of the methanogenic reactor. As expected, no methane forming or sulfate reducing bacteria were found in the acidogenic reactor. The populations of methanogenic bacteria were dominated by a mixed population of straight to curved rods and multicellular filaments which strongly resembled members of the genus Methanosaeta. Seven prevalent species of facultative anaerobic gram-negative bacteria were identified as Previdencia alcalifacienciens, Providencia rettgeri, Enterobacter cloaceae, Citrobacter freundii, Klebsiella oxytoca, Proteus pennri and Yersinia enterocolitica. The species Pseudomonas aeruginosa, Stenotrophomonas maltophila and Acinotobacter iwoffi, were the most frequently isolated glucose non-fermenting gram-negative bacilli. Among these species, only P. aeruginosa was present in high number in each sample.

Cassava starch effluent treatment with concomitant SCP production

Yeasts and yeast-like organisms were chosen for the aerobic treatment of cassava starch factory effluent. A mixed culture of Candida utills and Endomycopsis fibuliger efficiently and rapidly utilized both starch and free sugars. After 28 h fermentation the protein content of the biomass was 22% (w/w), which remained unchanged during the remainder of the fermentation (60 h). This treatment removed 94% of the COD and 91% of the BOD.

Anaerobic digestion of cassava starch factory effluent

Biomethanation of cassava starch factory effluent in a batch digester produced 130 l biogas/kg dry matter with an average melthane content of 59%. About 63% COD was removed during 60 days. In semicontinuous digesters, gas production was 3251/kg dry matter with a retention time of 33,3 days giving a COD reduction of 50%. Size of starter inoculum was important for good biogasification of the effluent.