Raw Cassava Research Articles

Kinetics, Thermodynamics, and Isotherms of Methylene Blue Adsorption Study onto Cassava Stem Activated Carbon

Water treatment using activated carbon is widely accepted, despite its high production cost. Therefore, this study was aimed to investigate the potential of cassava stem in activated carbon form for methylene blue (MB) dye uptake from water. Raw cassava stem (RCS) was also utilized to evaluate the difference between cassava stem in its raw form and after being converted to the activated carbon (ACS). The MB adsorption from water using the RCS and ACS was done in this study. The batch adsorption study showed fast MB uptake by ACS at 60 min contact time, while higher adsorbent dosage and higher pH contributed to higher adsorption percentage. The thermodynamic study showed positive values of ∆H° of ACS, indicating that the adsorption process of MB was endothermic. Meanwhile, the negative value of ∆G° showed that the adsorption processes of MB were spontaneous. The thermodynamic study showed higher fitting to Langmuir isotherm, with data from the kinetic study showing better pseudo-second-order equation fitting, which suggests the chemisorption process had happened. The highest adsorption recorded by ACS was 384.61 mg/g, indicating the possibility of cassava stem as the lower cost raw material for activated carbon production with excellent adsorption characteristics.

KERAGAAN AGROINDUSTRI KERIPIK SINGKONG DI KECAMATAN GEDONG TATAAN KABUPATEN PESAWARAN

The purposes of this research were to analyze the performance of cassava chips agroindustry reviewed from procurement of raw materials, labor productivity, production capacity, product quality, delivery speed, flexibility, and added value and income. The research used was a survey method. Research data collection was carried out in March 2019 in Gedong Tataan Subdistrict with the consideration that agro-industries were actively producing continuously and had the potency to be developed. The research locations were in three villages of cassava chips agro-industry centers, namely Karang Anyar Village, Bagelen Village, and Sungai Langka Village. Respondents were 14 cassava chips agro-industries. Raw material procurement, product quality, delivery speed, and flexibility were analyzed qualitatively descriptively. Productivity, production capacity, and income were analyzed quantitatively. Added value is analyzed using the Hayami method. The results showed that the procurement of raw cassava chips was correct in the type and quantity, while it was not correct in place. The average of productivity per month was 41.65 kg / HOK and the average of production capacity per month was 79%. Product quality and delivery speed were good enough, and flexibility was not optimal. The agroindustry had a positive added value, profit with R/C>1, and the average of income per month of IDR 7,613,146.29.Key words: agroindustry, cassava chips, performance

Improving the Nutritional Values of Cassava Pulp Through Supplementation of Selected Leaves Meal and Fermentation with Chrysonilia Crassa

This study evaluated the impact of fermentation with Chrysonilia crassa on nutritional composition and antioxidative activity of the mixture of cassava pulp and selected leaves meal. Cassava pulp (60 g) was mixed thoroughly with 35 g leaves meal of either cassava, M. Oleifera, or L. leucocephala, and inoculated with Chrysonilia crassa starter (5 g). The mixture was aerobically incubated for 3 days at room temperature and analyzed for the proximate composition, gross energy, true protein, antioxidant activity, and amino acid content. The fermented products showed higher crude protein, ether extract, ash, and gross energy but lower fibre content than unfermented cassava pulp. Both leaves meal supplementation and fermentation increased the true protein content of cassava pulp. Superior antioxidant activities and higher amino acids were observed in the fermented products than raw cassava pulp. In conclusion, supplementation of leaves meal in conjunction with Chrysonilia crassa-fermentation improved the nutritional values and antioxidant potential of cassava pulp.

Iodine status in women attending Mnazi Mmoja Hospital in Zanzibar: a matched case-control study

BackgroundIodine deficiency can have adverse health effects in all age groups affecting growth, development and cognitive functions as well as the incidence of goitre. Worldwide, the most important dietary source...

The Urgency of Institutional Development of Cassava Industry in Daerah Istimewa Yogyakarta and Jawa Tengah

The study shows that there was variation in the process of cassava-based food production. In Daerah Istimewa Yogyakarta (DIY) and Central Java, the farming systems were still subsistence oriented as the members still carried out traditional farming and worked without practicing intensive farming. However, the cassava-based food processing had already been commercially oriented. Some farmers have successfully collaborated with the larger cassava industry who were profit and commercially oriented. Some agribusiness units required specific varieties, but others opened to any varieties of cassava. The various arrangements have created different patterns of partnership. There were three types of business partnerships namely (1) growers and small-scale manufacturers; (2) partnership among growers, raw material processors, food manufacturers, and distributors or sellers; and (3) partnership among growers, small or large manufacturers and distributors or sellers. Among those three patterns, some enterprises had already performed a business-oriented processing method and quality assurance which requires best quality of raw cassava. This is resulted in a better selling price. Business partnerships can guarantee the sustainability of business relationships among business units. A better upstream-downstream relation needs to be developed to prevent the risks of raw materials supply.

Sustainability of Garri Processing: A Case Study of Ogun State, Nigeria

Garri is one of the most developed and convenient staple food commodities been produced from cassava in West Africa. To select the best method, garri production technology has been produced at different levels, this includes grating, fermentation, and dewatering. Producer of garri and edible starch is faced with the problem of the product price, limited information, and inadequate capital, lack of equipment, poor road, inadequate labour and water supply, long waiting time during grating, and some stages of processing. Limitation experienced by cassava processor includes lack of capital, inadequate power supply, the short lifespan of raw cassava tuber, long fermentation process, high cost of transportation, unstable price of garri. Result obtained from the constraints limiting garri processing in owode-yewa of Ogun state revealed that the short life span of raw cassava tubers is the most severe with 98%. This rating was followed by the unstable price of garri with 92%, long fermentation process with 67%, high transportation cost of inputs with 63%, while the lowest is the lack of access to information with an 8% plant layout. This study was able to provide scheduling operation of garri processing, the process of operation, maintenance of operation, plant layout, and come up with results that can be useful for other processing units in other countries.

Single-step ethanol production from raw cassava starch using a combination of raw starch hydrolysis and fermentation, scale-up from 5-L laboratory and 200-L pilot plant to 3000-L industrial fermenters

BackgroundA single-step ethanol production is the combination of raw cassava starch hydrolysis and fermentation. For the development of raw starch consolidated bioprocessing technologies, this research was to investigate the optimum conditions and technical procedures for the production of ethanol from raw cassava starch in a single step. It successfully resulted in high yields and productivities of all the experiments from the laboratory, the pilot, through the industrial scales. Yields of ethanol concentration are comparable with those in the commercial industries that use molasses and hydrolyzed starch as the raw materials.ResultsBefore single-step ethanol production, studies of raw cassava starch hydrolysis by a granular starch hydrolyzing enzyme, StargenTM002, were carefully conducted. It successfully converted 80.19% (w/v) of raw cassava starch to glucose at a concentration of 176.41 g/L with a productivity at 2.45 g/L/h when it was pretreated at 60 °C for 1 h with 0.10% (v/w dry starch basis) of Distillase ASP before hydrolysis. The single-step ethanol production at 34 °C in a 5-L fermenter showed that Saccharomyces cerevisiae (Fali, active dry yeast) produced the maximum ethanol concentration, pmax at 81.86 g/L (10.37% v/v) with a yield coefficient, Yp/s of 0.43 g/g, a productivity or production rate, rp at 1.14 g/L/h and an efficiency, Ef of 75.29%. Scale-up experiments of the single-step ethanol production using this method, from the 5-L fermenter to the 200-L fermenter and further to the 3000-L industrial fermenter were successfully achieved with essentially good results. The values of pmax,Yp/s, rp, and Ef of the 200-L scale were at 80.85 g/L (10.25% v/v), 0.42 g/g, 1.12 g/L/h and 74.40%, respectively, and those of the 3000-L scale were at 70.74 g/L (8.97% v/v), 0.38 g/g, 0.98 g/L/h and 67.56%, respectively. Because of using raw starch, major by-products, i.e., glycerol, lactic acid, and acetic acid of all three scales were very low, in ranges of 0.940–1.140, 0.046–0.052, 0.000–0.059 (% w/v), respectively, where are less than those values in the industries.ConclusionThe single-step ethanol production using the combination of raw cassava starch hydrolysis and fermentation of three fermentation scales in this study is practicable and feasible for the scale-up of industrial production of ethanol from raw starch.

PREPARATION OF CASS-SOYA CONCENTRATE FOR INCLUSION IN POULTRY DIETS (IN-VITRO STUDIES)

ABSTRACT 
 A study was conducted to determine the best means of processing cassava and soybeans together in a suitable proportion to produce a concentrate of good physical and nutritive quality for feeding to poultry. Samples of cassava and soybeans were subjected to six different processing techniques and mixed together in different proportions viz. 80:20, 60:40 or 50:50. The processing techniques were as follows; toasted soybeans and dried cassava chips were mixed together and ground in sample A while toasted soybeans and cassava were ground separately before mixing in sample B. Samples C and D included raw cassava and soybeans mashed together before being sun-dried or oven dried respectively. For samples E and F raw cassava and soybeans were boiled together before being sun-dried or oven-dried respectively. Results showed that when cassava and soybeans were boiled together and dried, the product was of good physical texture as indicated by its flaky texture. Nutritive quality was also high in terms of protein and energy contents. For these samples, sun drying was preferred to oven-drying due to the ease of the method of drying as well as the cheaper cost involved in drying. Proportions of either 50:50 or 60:40 are preferred to take advantage of both energy and protein contents of the final product.Reasonable prices have stimulated poultry production. In Nigeria, however, the major crops for livestock feeding being corn, soybeans and groundnut are widely used for human consumption... Hence there is increasing.

Effects of 5-hour wetting of sun-dried cassava tuber meal on the HCN content and dietary value of the meal for young broiler chicks

The efficacy of wetting sun-dried cassava tuber meal as a method of reducing its hydrocyanide (HCN) content and improving its nutritive value for broilers was investigated. Cassava tubers were peeled, chopped into pieces, sun dried and then milled. Part of the sun-dried cassava tuber meal was soaked in water at the rate of 5 parts of water to 4 parts of the meal, thinly spread on the floor for 5 hours and then taken out and spread by the side of the tarred road and sun-dried again. The raw cassava tuber meal (RCTM), sun-dried cassava tuber meal (SCTM) and wetted sun-dried cassava tuber meal (WSCTM) were analysed for cyanide conteni. Five diets were made such that dier / (control) contained no cassava tuber meal; in diets 2 and 3, 75% of the maize in diet I was replaced with SCTM and WSCTM, respectively, while in diets 4 and 5, 100% of the maize was replaced with SCTM and WSCTM, respectively. Each diet was fed to a group of 30 one-week old broiler chicks for 4 weeks. Blood was collected from the birds at the end of the feeding trial and haematological constituents determined. RCTM contained 800ppm HCN, SCTM contained 50ppm and WSCTM contained 10ppm. At 100% replacement of dietary maize with SCTM, growth performance of the birds was significantly (P <0.05) depressed. HB, PCV, RBC and WBC were also depressed at that level. Wetting sun-dried cassava tuber meal appeared to be a simple and effective way of processing cassava for use as energy feed for broiler production.

A review of cassava semolina (gari and eba) end-user preferences and implications for varietal trait evaluation.

The purpose of this review is to support breeders and food scientists by examining research carried out on end-user preferences for gari and its derived dough product, eba, in Africa. The review focused on gari regarding the physical and chemical composition of raw cassava roots, methods of storage, the composition of gari with or without enrichment, and the sensory evaluation of gari and eba. The primary sensory attributes identified to describe gari are colour, taste, texture, aroma and flavour. Texture attribute of importance is crispiness for uncooked gari, and hand feel before consumption for eba. There was a significant correlation between the sensory characteristics of gari and the starch and cyanogenic potential (CNP) contents of the raw roots. Hence, the correlation of the end-user preferences with the chemical composition of the cassava roots could be helpful to breeders in refining selection criteria and developing high-throughput screening methods.

ARTP/EMS-combined multiple mutagenesis efficiently improved production of raw starch-degrading enzymes in Penicillium oxalicum and characterization of the enzyme-hyperproducing mutant

BackgroundApplication of raw starch-degrading enzymes (RSDEs) in starch processing for biofuel production can effectively reduce energy consumption and processing costs. RSDEs are generally produced by filamentous fungi, such as Penicillium oxalicum, but with very low yields, which seriously hampers industrialization of raw starch processing. Breeding assisted by random mutagenesis is an efficient way to improve fungal enzyme production.ResultsA total of 3532 P. oxalicum colonies were generated after multiple rounds of mutagenesis, by atmospheric and room-temperature plasma (ARTP) and/or ethyl methanesulfonate (EMS). Of these, one mutant A2-13 had the highest RSDE activity of 162.7 U/mL, using raw cassava flour as substrate, a yield increase of 61.1%, compared with that of the starting strain, OXPoxGA15A. RSDE activity of A2-13 further increased to 191.0 U/mL, through optimization of culture conditions. Increased expression of major amylase genes, including the raw starch-degrading glucoamylase gene, PoxGA15A, and its regulatory gene, PoxAmyR, as well as several single-nucleotide polymorphisms in the A2-13 genome, were detected by real-time reverse transcription quantitative PCR and genomic re-sequencing, respectively. In addition, crude RSDEs produced by A2-13, combined with commercial α-amylase, could efficiently digest raw corn flour and cassava flour at 40 °C.ConclusionsOverall, ARTP/EMS-combined mutagenesis effectively improved fungal RSDE yield. An RSDE-hyperproducing mutant, A2-13, was obtained, and its RSDEs could efficiently hydrolyze raw starch, in combination with commercial α-amylase at low temperature, which provides a useful RSDE resource for future starch processing.

Protein Enrichment of Cassava-Based Dried Distiller’s Grain by Solid State Fermentation Using Trichoderma Harzianum and Yarrowia Lipolytica for Feed Ingredients

Cassava-based dried distiller’s grain (Cassava-based DDG) is known as a by-product of the bio-ethanol industry with low nutritional value due to the presence of cyanide and to the low content of protein. More value can be added to cassava-based DDG through solid-state fermentation (SSF) using mold and yeast. SSF were conducted with cassava-based DDG in 8 and 5 days of fermentation, respectively. Under optimal conditions, the crude protein fraction of cassava-based DDG fermented by Trichoderma harzianum BiomaTH1 or Yarrowia lipolytica W29 was increased from 11.84% DM for unfermented sample to 15.29 and 14.06% DM, respectively. In addition, the total amino acids of fermented samples using T. harzianum and Y. lipolytica was increased from 11.01% DM to 13.86% DM and 12.39% DM along with an increase in the essential amino acids content which enhanced by 55% and 22%, respectively, including limiting amino acids in pig feeds. The in vitro protein digestibility was improved significantly from 82.5% to 89.2 and 86.9% for T. harzianum and Y. lipolytica fermentation, respectively. Beside increasing the nutritional value, the SSF showed a clear effect in reducing cyanide content of raw cassava DDG from 62.3 mg/kg DM to 24.3 and 53.6 mg/kg. The obtained results indicated that the protein enrichment of this bio-ethanol by-product using mold and yeast fermentation could be very promising to be used efficiently as a cheap and abundant source of essential amino acids for animal feed ingredients in Vietnam. The nutritional projection of adding this cheap ingredient was discussed.

From cassava to gari: mapping of quality characteristics and end-user preferences in Cameroon and Nigeria.

User's preferences of cassava and cassava products along the value chain are supported by specific root quality characteristics that can be linked to root traits. Therefore, providing an evidence base of user preferred characteristics along the value chain can help in the functional choice of cassava varieties. In this respect, the present paper presents the results from focus group discussions and individual interviews on user preferred quality characteristics of raw cassava roots and the derived product, gari, - one of the major cassava products in Sub-Saharan Africa - in major production and consumption areas of Cameroon and Nigeria. Choice of cassava varieties for farming is mainly determined by the multiple end uses of the roots, their agricultural yield and the processing determinants of roots that support their major high-quality characteristics: size, density, low water content, maturity, colour and safety. Processing of cassava roots into gari goes through different technological variants leading to a gari whose high-quality characteristics are dryness, colour, shiny/attractive appearance, uniform granules and taste. Eba, the major consumption form of gari in Cameroon and Nigeria, is mainly characterised by its textural properties: smoothness, firmness, stickiness, elasticity and mouldability. Recommendations are made, suggesting that breeding will have to start evaluating cassava clones for brightness/shininess, as well as textural properties such as mouldability and elasticity of cassava food products, for the purpose of supporting decision-making by breeders and the development of high-throughput selection methods of cassava varieties. Women are identified as important beneficiaries of such initiatives giving their disadvantaged position and their prominent role in cassava processing and marketing of gari.

PRODUCTION OF POLY(3-HYDROXYBUTYRATE) FROM RAW CASSAVA STARCH BY Bacillus megaterium D8

Biosynthesis of polyhydroxyalkanoate (PHA) from raw cassava starch as the carbon source by bacteria was investigated in this study. About 300 bacterial colonies were isolated from soil samples. Among them, sixteen bacterial strains were found to produce PHA from cassava starch. Strain D8 produced the highest poly(3-hydroxybutyrate) (PHB) content of 69.8 wt% was selected for further studies. Strain D8 was classified under the Bacillus megaterium group based on 16S rRNA gene sequences. High cell dry weight (CDW) of 6.5 g\L and poly(3- hydroxybutyrate) (PHB) content of 66.2 wt% were obtained by strain D8 after 21 h of cultivation in a bioreactor using batch culture mode. In this study, Bacillus megaterium D8 exhibited high promise for reducing the production cost of PHB.

Very high Gravity (VHG) Bioethanol Production Using Modified Simultaneous Saccharification and Fermentation of Raw Cassava Chips with Molasses by Kluyveromyces marxianus DMKU-KS07

Purpose: The aim of this study was to investigate the enhancement of very high gravity (VHG) bioethanol production using co-substrates of cassava chip hydrolysates and molasses by Kluyveromyces marxianus DMKU-KS07. Methods: The factors effecting cassava chip hydrolysis by raw starch degrading enzyme (RSDE) from the thermophilic bacterium Laceyella sacchari LP175 and commercial glucoamylase were investigated. The obtained raw cassava chip hydrolysate was co-fermented with molasses by the thermotolerant K. marxianus DMKU-KS07 at 42°C under nonsterile system. Results: Factors affecting sugar syrup production from raw cassava chips by synergistic hydrolysis and enzyme saccharification were optimized at temperature, substrate concentration and agitation rate of 50 °C, 250 g/L and 200 rpm, respectively. A yield of 98.6 g/L was obtained at 6 h of incubation, equivalent to 45.9% saccharification and 51.4% hydrolysis of starch, respectively. High bioethanol concentration at 118 g/L, with highest productivity of 2.19 g/L/h and ethanol yield (YP/S) at 0.44 g EtOH/g total sugar, equivalent to 86.3% theoretical yield, was obtained by modified simultaneous saccharification and fermentation (Modified SSF) with co-fermentation of substrates from the enzymatic hydrolysates of raw cassava chips at 42 °C for 12 h. Subsequent addition of molasses increased the final concentration to 100 g total sugar/L at 36 h. Conclusions: Co-fermentation of raw cassava chip hydrolysates with molasses enhanced production of bioethanol at VHG condition, and showed potential for application in ethanol production by enhancing the fermentation process and reducing energy consumption.

Review on Effect of Processing on Cassava Anti-Nutritional Factors and Impacts on Health

Cassava is a valuable source of food for developing countries, Different processing techniques exist to remove cyanogens andt heir effectiveness depends on the processing steps and the sequence utilized, and it often is time-dependent. The proximate composition of raw and boiled cassava tubers was not significantly different (P> 0.05), except in moisture, fat, carbohydrate and Energy value. High levels of the antinutrients in raw cassava tubers (20.56mg/100g Tannins; 1,16mg/100g oxalate and 3.36mg/100g phytate) make them unsafe and unsuitable for human consumption except after processing. Crushing and sun-drying cassava roots made into flour removes 96% to 99% of total cyanogens, whereas soaking and sun-drying into lafun or fufu, or soaking and fermenting and roasting into gari or farina, removes about 98% of cyanogens. For cassava leaves, which have 10 times more cyanogens than roots, pounding and boiling in water is an efficient process to remove about 99% of cyanogens. Other strategies to reduce toxicity include development of low-cyanogen cassava varieties and cassava transgenic lines with accelerated cyanogenesis during processing. Fermentation and oven-drying are efficient processing methods to remove phytate (85.6%) and polyphenols (52%), respectively, fromcassava roots. Sun-drying the leaves, with or without prior steaming or shredding, removes about 60% phytate. Cassava is a nutritionally strategic famine crop for developing countries and, therefore, reducing its toxicity and improving its nutritional value is crucial.

Intensive Multiple Sequential Batch Simultaneous Saccharification and Cultivation of Kluyveromyces marxianus SS106 Thermotolerant Yeast Strain for Single-Step Ethanol Fermentation from Raw Cassava Starch

We developed the intensive multiple sequential batch simultaneous saccharification and cultivation of the selected thermotolerant yeast strain for single-step ethanol production. The selection and high-cell-density inoculum production of thermotolerant yeast able to produce ethanol under the optimal conditions for single-step ethanol fermentation has become a necessity. In this study, the newly isolated Kluyveromyces marxianus SS106 could tolerate high temperatures (35–45 °C) and grow under a wide range of pH values (3.0–5.5), which are the optimum conditions of raw cassava starch hydrolyzing enzyme used in single-step ethanol fermentation. The high-cell-density concentration of K. marxianus SS106 was produced by a single batch and an intensive multiple sequential batch process in a 5-L stirred tank bioreactor using the simultaneous saccharification and cultivation (SSC) method. The single SSC process yielded the yeast cell biomass at a concentration of 39.30 g/L with a productivity of 3.28 g/L/h and a specific growth rate of 0.49 h−1. However, the yeast cell density concentration was higher in the intensive multiple sequential batch SSC than in the single batch process. This process yielded yeast cell biomass at concentrations of 36.09–45.82 g/L with productivities of 3.01–3.82 g/L/h and specific growth rates of 0.29–0.44 h−1 in the first six batch cycle. The results suggested that the intensive multiple sequential batch simultaneous saccharification and cultivation of K. marxianus SS106 would be a promising process for high-cell-density yeast production for use as the inoculum in single-step ethanol fermentation. Furthermore, we also experimented with single-step ethanol production from raw cassava starch by K. marxianus SS106 in a 5-L stirred tank fermenter. This produced ethanol at a concentration of 61.72 g/L with a productivity of 0.86 g/L/h.

Effect of Formulation Technology on Characteristics and Prices of Cassava Instant Noodles Seasoning Gluten Free

The level of dependence of Indonesian people on noodles from raw materials is very high and is increasing. One potential to reduce the level of dependence of Indonesian people on flour products is by processing and optimizing the local resource base in the form of cassava as a raw material for making gluten free noodles. To increase the added value of the gluten free cassava noodle product by processing it into an instant noodle package in which seasoning flour is added. The purpose of this research activity is to influence the formulation on chemical characteristics, organoleptics and prices of instant gluten free instant noodles with raw cassava flour. The study design used a completely randomized design and was carried out using two replications. The analysis results were processed using SPSS 2.1 software. Whereas the price calculation is based on the results of the practical calculation of the concentration of the use of formula and is calculated manually. The four instant gluten free cassava seasoning powder formulas showed significantly different results with a significant level of 95% for the parameters of water content, ash, protein, and carbohydrate. The seasoning flour for formula D has the highest levels of NaCl compared to other formulas. While the lowest levels of NaCl are found in formula B, which is 45.25%. Based on the results of the analysis of the cost calculation for the making of seasoning flour for gluten free instant cassava products, formula B has the smallest value of processing costs.

Simultaneous amylase production, raw cassava starch hydrolysis and ethanol production by immobilized Aspergillus awamori and Saccharomyces cerevisiae in a novel alternating liquid phase–air phase system

As a solution to the problems of mass transfer limitation in submerged cultures and scale up of solid-state/liquid-surface cultures, an alternating liquid phase–air phase bioreactor was developed. It consisted of a bioreactor equipped with a siphon system and a reservoir. Aspergillus awamori was immobilized in loofa sponge inside the bioreactor and culture broth was pumped from the reservoir into the bioreactor. Each time the culture broth level reached a critical level, the broth automatically siphoned back into the reservoir. Thus the immobilized cells were alternatingly submerged and exposed to air. The duration of each phase was controlled by the pumping rate and with an on-off timer. During amylase production from soluble starch and raw cassava starch, the optima ratios of the liquid to air phases were 12 h : 12 h and 3 h : 6 h respectively. Saccharomyces cerevisiae IR2 was immobilized in the reservoir and the system was used for simultaneous amylase production, hydrolysis and ethanol production from raw cassava starch. The process was very stable for more than 7 batches with high ethanol yield of 0.46 g-ethanol/g-starch and productivity of 1.73 g-ethanol/L/h. These values are high, the system can be scaled up, and thus it has many potential applications.

Assessment of cassava peels as renewable substrate for production of poly-γ-glutamic acid by Bacillus subtilis

Poly-γ-glutamic acid (γ-PGA) is a polymeric substance with diverse applications as thickening, anti-freezing, sticking and bitterness relieving agent. This study was aimed at utilizing cassava peels as the major substrate for production of γ-PGA by Bacillus subtilis. Pretreatment of the cassava peels was carried out using alkali, acid and organosolv methods. Effects of different carbon, nitrogen and process parameters were subjected to one-factor-at-a-time method. The raw cassava peel gave significantly (p < 0.05) higher yield of γ-PGA of 3.20 ± 0.08 mg/g when compared with all the other pretreated samples. The highest yield of γ-PGA (6.23 ± 0.13 mg/g) was obtained in a medium containing 1% (w/w) citric acid and 0.5% (w/w) (NH4)2SO4, initial moisture content 65%, inoculum concentration at 2% and incubation time of 4 days at 35 °C. Following the FTIR analysis, γ-PGA samples showed characteristic amide absorption at ~ 3753.4 cm−1, carbonyl absorption at 1600–1636.4 cm−1, and hydroxyl absorption at 3200–3276.3 cm−1. The relative viscosity (9.92 ± 0.06 mPas), and melting point (193 ± 0.04 °C) were found to be comparable with the values obtained for commercially available γ-PGA. This study demonstrates that cassava peels can be utilized as renewable raw material for production of γ-PGA by B. subtilis.