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Physico-chemical characterization of fermented ricebran biomass Caracterización fisico-química de labiomasa del salvado de arroz fermentadoM. dos S. Oliveira a , V. Feddern a , L. Kupski a , E. P. Cipolatti a , E. Badiale-Furlong a &L. A. de Souza-Soares aa Laboratório de Ciência de Alimentos, Escola de Química e Alimentos , UniversidadeFederal do Rio Grande (FURG), Rua Eng , Alfredo Huch, 475, Pav. 06, Centro, CEP96201–900, Rio Grande – RS, BrasilPublished online: 23 Sep 2010.

To cite this article: M. dos S. Oliveira , V. Feddern , L. Kupski , E. P. Cipolatti , E. Badiale-Furlong & L. A. de Souza-Soares(2010) Physico-chemical characterization of fermented rice bran biomass Caracterización fisico-química de la biomasa delsalvado de arroz fermentado, CyTA - Journal of Food, 8:3, 229-236, DOI: 10.1080/19476330903450274

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Physico-chemical characterization of fermented rice bran biomass

Caracterizacion fisico-quımica de la biomasa del salvado de arroz fermentado

M. dos S. Oliveira*, V. Feddern, L. Kupski, E.P. Cipolatti, E. Badiale-Furlong and L.A. de Souza-Soares

Laboratorio de Ciencia de Alimentos, Escola de Quımica e Alimentos, Universidade Federal do Rio Grande (FURG), Rua Eng.Alfredo Huch, 475, Pav. 06, Centro, CEP 96201–900, Rio Grande – RS, Brasil

(Received 10 June 2009; final version received 26 October 2009)

The experiment was conducted to evaluate the fermentation effect with Rhizopus oryzae in the composition of wholerice bran, which was used as substratum for the fermentative procedure in tray bioreactors at 30 8C for 120 h. Duringthe fermentation, samples were withdrawn in different times (0, 24, 48, 72, 96, and 120 h) for physico-chemicaldetermination using standard procedures. Reductions in moisture, fat, phytic acid, and reducing sugars content ofrice bran were respectively 24.6%, 40%, 50%, and 60%. The fermented bran presented an increase of 30% in ashcontent, 50% in fibers, and 40% in proteins. The digestible amino acid determination indicated 27.6% increase in thedigestibility of produced proteins.

Keywords: Rhizopus oryzae; solid-state fermentation; rice bran; protein; phytic acid; digestible amino acid

El experimento fue llevado a cabo para evaluar el efecto de la fermentacion con Rhizopus oryzae en la composicionde salvado de arroz, el cual fue usado como sustrato para el proceso de fermentacion en biorreactores de bandeja a30 8C durante 120 horas. Durante la fermentacion, se tomaron muestras en diferentes momentos (0, 24, 48, 72, 96 y120 h) para su determinacion fısico-quımica usando metodos estandar. La reduccion en contenido de humedad,grasa, acido fıtico y azucares reductores del salvado de arroz fueron respectivamente 24,6%, 40%, 50% y 60%. Elsalvado fermentado presento un incremento en 30% de contenido de cenizas, 50% de fibras y 40% de proteınas. Ladeterminacion de aminoacidos digeribles indico un aumento de 27,6% en la digestibilidad de proteınas producidas.

Palabras clave: Rhizopus oryzae; fermentacion en estado solido; salvado de arroz; proteına; acido fıtico; aminoacidosdigeribles

Introduction

The agroindustrial sectors produce a great amount ofwastes, residues, and by-products which can berecovered and often upgraded to higher value anduseful products. Wastes increase pollution problemsand represent a loss of valuable biomass and nutrients.In opposition of what happened in the past, currently,concepts of minimization, by-product recovery, andbioconversion of residues are more and more spreadout and necessary for the agroindustrial chains(Laufenberg, Kunz, & Nystroem, 2003).

The use of fermentative processes, which impliesemploying microorganisms to get resultant transfor-mations of their metabolic activity, is among the formsto increase the availability of nutrients in raw materials(Pelizer, Pontieri, & Moraes, 2007). Amongst theseprocesses, the solid-state fermentation has beenadopted in recent years, for the biotechnologicalindustry, due to its potential application in theproduction of the active secondary metabolites, forthe industries of animal food, fuel, foods, chemical

and pharmaceutical, conferring aggregate value toresidues not or underutilized (Singhania, Patel, Soccol,& Pandey, 2009).

The fungi are among the more appropriate micro-organisms utilized in solid fermentation, as they canproduce a variety of biochemical products, many ofwhich are required for their proper growth andmetabolism. They also produce secondary metabolitesfrequently in the stationary phase, thanks to theirability of reproducing in low water activity environ-ments (Esposito & Azevedo, 2004).

The fungi of the Rhizopus genera are classified aszygomycetes, of the Mucorales order and they areconsidered the most primitive fungi (Esposito &Azevedo, 2004; Pitt & Hocking, 1997). Some species,such as R. oryzae, R. oligosporus, and R. stolonifer, canproduce enzymes, such as phytases, lipases andglucoamylases and others, mainly using agroindustrialresidues as solid medium for their development(Ramachandran, Roopesh, Nampoothiri, Szakacs, &Pandey, 2005; Sabu et al., 2002). Characteristically,

*Corresponding author. Email: mel_olisa@yahoo.com.br

CyTA – Journal of FoodVol. 8, No. 3, November 2010, 229–236

ISSN 1947-6337 print/ISSN 1947-6345 online

� 2010 Taylor & Francis

DOI: 10.1080/19476330903450274

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this genera of fungi does not include toxic species,being Generally Recognized As Safe (GRAS) by theFood and Drug Administration (FDA).

Rice is amongst the original sources of residues thatcan be called by-products. Rice milling results in 5 to8% of rice bran. The 2007/2008 rice harvest in RioGrande do Sul – Brazil was of 7.5 million tons, with anestimated record harvest in 2009 (www.irga.rs.gov.br,2008). This production generates consequently, 0.4–0.6million tons of rice bran. This bran contains between11 and 13% of basic protein, *11.5% of crude fiber,being able to reach 20% of its weight in oil, andantioxidant and functional components (Silva,Sanches, & Amante, 2006).

Rice bran is the subject of different researches in thearea of feed, oil components extraction, proteinextraction, and due to its low cost and abundance, itpresents great potential to be used in biotechnologicalprocesses in obtaining metabolites of interest (Adebiyi,Adebiyi, Jin, Ogawa, & Muramoto, 2007; Chandi &Sogi, 2007; Pandey, Szakacs, Soccol, Rodriguez-Leon,& Soccol, 2001; Vali, Ju, Kaimal, & Chern, 2005; Yun& Hong, 2007).

The objective of this work was to evaluate theeffect of R. oryzae in physico-chemical characteristicsof rice bran applied as substratum in a solid-statefermentation process, aiming to identify the potentialof chemical components from fermented biomass.

Materials and methods

Rice bran

The rice bran used was supplied by a rice institutenamed IRGA (Instituto Rio Grandense de Arroz),located in Rio Grande do Sul, Brazil. The bran waspacked in polypropylene bags of 5 kg, being kept at thetemperature of 710 8C, until the moment of its use inthe fermentative process. The rice bran preparation, asa substrate of the solid-state fermentative process,consisted of standardizing its granulometry between0.35 and 0.60 mm, using an electromagnetic agitator(Bertel) of 60 Hz, equipped with sieves of differentmeshes.

Solid-state fermentation

Inoculum preparation

The strain of R. oryzae, used as fermentative agent,was isolated from rice bran and identified in theLaboratory of Microbiology at the Food ProcessingCenter of the Passo Fundo University, RS, Brazil.The cultures were kept at 4 8C in potato-dextroseagar medium and the spores were scraped from theslopes into aqueous emulsion of Tween 80 (0.2%). Thesame medium was used for spores incubation during7 d at 30 8C until new and complete sporulation of thefungi in the culture. Spores were enumerated inNeubauer chamber.

Fermentation

The fermentationwas carried out in tray bioreactors, withdimensionsof 2961765.5 cm3.The ricebran substratum(100 g)wasplaced inbioreactors, in the formofafine layerof *2 cm, after the substratum homogenization with45 mL of the saline solution (KH2PO4 2 g L71, MgSO4

1 g L71, NH2CONH2 1.8 g L71 in HCl 0.4 M). Braninitial spores concentration was 4.06106 spores g71

(Badiale-Furlong, Cacciamani & Garda-Buffon, 2007).According to Hasan, Costa, and Sanzo (1998), themoisture was adjusted to 50% with sterilized wateraddition and trays were covered with sterilized gauze toallow aeration, before being incubated at 30 8C for 120 h.To carry out physico-chemical characterization, sampleswere withdrawn at the beginning of the process and each24 h, being stored at718 8C.

Physico-chemical characterization of fermented biomass

Proximate composition

The moisture, ash, and fat determination weregravimetrically determined, according to conditionsrecommended by AOAC (2000). The total proteincontent was determined as total nitrogen, by Kjeldahlmethod, described in AOAC 2000 (955.04C), using theprotein conversion factor of 6.25. The crude fibers weredetermined through gravimetrical measurement of theresidue obtained by the acid and basic digestion of thesamples. The residue ashes were estimated, followingthe recommendations of the coordinated collaborativestudy by the Ministry of Agriculture, Livestock andProvisioning (1991).

Reducing sugars content

The sample (10 g) added of 40 mL of distilled water wastaken to a 50 8Cwater-bath for 30 minwith agitation. Thesolution was filtered, and 10 mL of Carrez I solutionmixed with 10 mL of Carrez II solution were addedmaking up the volume to 100 mLwith distilledwater. Theliquid and flocculated phases were separated by centrifu-gation at 2800g. An aliquot (1 mL) of the supernatant,added with 1 mL of 2 MHCl, was kept in a 50 8C water-bath for 40 min. The mixture was neutralized with 2 MNaOH, being the colorimetrical reaction carried out withaddition of 1 mL dinitrosalicylic acid (DNS), completingto a final volume of 10 mL. The absorbances weremeasured in a UV–Visible spectrophotometer (modelCary 100, Varian, Palo Alto, CA, USA) at 546 nm. Aglucose standard curve of concentration between 0.01and 0.1 mg mL71 was used for quantification (Miller,1959).

Digestible amino acid content

The digestible amino acid content was estimated afterenzymatic hydrolysis of the biomass protein with

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pepsin (specific activity of 56.7 mgtyrosine min71

mgprot71) and pancreatin (specific activity of 320

mgtyrosine min71 mgprot71). The sample (2.5 g) was

dissolved in 10 mL pepsin solution and agitated (90rpm) at 37 8C for 3 h. Finally, the pH of the samplewas elevated to 7.0 and 10 mL of pancreatin solutionwas added (1.5 mg mL71 phosphate buffer pH 8.0).The samples were kept under orbital agitation (130rpm) at 37 8C for 24 h. After hydrolysis, the undigestedfraction was separated by centrifugation (2800g) andfiltration (Silveira & Badiale-Furlong, 2007). Thefiltrated fraction (10 mL) was mixed with 10 mL of40% TCA solution and remained at rest for 1 h inrefrigeration temperature (4 8C). After that period, themixture was centrifuged and filtrated. The secondfiltrate was diluted for released amino acids determina-tion using the Lowry, Rosenbough, Fair, and Randall(1951) method. The absorbance was measured in aUV–Visible spectrophotometer (model Cary 100,Varian, Palo Alto, CA, USA) at 660 nm and theamino acid content estimated by a standard tyrosinecurve varying from 1.6 to 15 mg mL71.

Phytic acid content

The phytic acid extraction was carried out with 5 g ofsample and 50 mL of 0.8 M HCl solution under orbitalagitation (130 rpm) for 1 h. The mixture was separatedby centrifugation at 2800g for 10 min. The supernatantwas eluted in ion-exchange chromatography column (thestationary phase was prepared with 0.50 g of Dowex-AGX-4 resin dissolved in 5 mL of deionized water,conditioned in the column and eluted with 10 mL ofdeionized water, 10 mL of NaCl 0.7 M solution andagain with 10 mL of deionized water). Sample of 1 mLof the supernatant was diluted to 25 mL with deionizedwater, of which 2 mL were eluted in the column with10 mL of NaCl 0.1 M solution, followed by 10 mL ofNaCl 0.7 M solution. The last aliquot was collected and3 mL of the eluate reacted with 1 mL of the Wadereagent (ferric chloride 0.03% and sulfosalicylic acid0.3%). The absorbance was measured at 500 nm in aUV–Visible spectrophotometer (model Cary 100, Var-ian, Palo Alto, CA, USA). The concentration of phyticacid standard curve varied between 6.6 and 39.8 mgmL71 (Latta & Eskin, 1980).

Statistical analysis of data

The data generated from this study were subjected to aone-way analysis of variance (ANOVA) at 5% level ofsignificance. Means were compared by Tukey test. Allthe determinations were carried out in duplicates.

Results and discussion

The granulometry is an important factor in the physico-chemical determinations; therefore it can influence in

the efficiency of the extraction methods of studiedcomponents, and also allow the standardization of therice bran as medium for the solid-state fermentation.The granulometry effect, heat transference, and otherparameters of process were studied by Hasan et al.(1998) and the results showed that this affects fermen-tative process development. Table 1 shows the ricebran granulometry distribution used as fermentationsubstratum.

For the experiment, the fractions from Tyler 24 to42 were chosen. The removal of bran fractions withgranulometry less than 0.355 mm avoids mediumcompaction during fermentation. The bran fractionremoved in Tyler 14 consisted of endosperm fragmentsand rice hulls. They could cause analytical errors andnot uniform chemical composition.

Several authors point out that the growth ofmicroorganism on a substrate can change its chemicalcomposition due to the production of exocellularenzymes to obtain nutrients, in addition, productionof other metabolites. This metabolism can enrich thesubstrate, depending on the intrinsic components ofthe fermentation agent or by nutrients availabilitypresented in the substrate. The microbial action turnsthe substrate components available to chemical orenzymatic extractive processes (Blandino, Al-Aseeri,Pandiella, Cantero, & Webb, 2003; Olanipekun,Otunola, Adelakun, & Oyelade, 2009; Othman,Roblain, Chammen, Thonart, & Hamdi, 2009; Paredes-Lopes, Gonzalez-Castaneda, & Carabez-Trejo, 1991;Prinyawiwatkul, Beuchat, Mcwatters, & Phillips, 1996).

Table 2 shows the rice bran physico-chemicalcomposition before and during the fermentativeprocess by R. oryzae. The results were expressed indry basis (db).

Among the authors who mentioned the R. oryzaeaction, Amadioha (1998) found that R. oryzae growthcaused a decrease in starch, maltose, sucrose, proteinand lipid content from stored potatoes. Badiale-Furlong, Cacciamani, and Garda-Buffon (2007) foundfor rice bran that the action of Rhizopus spp. reduced

Table 1. Rice bran granulometry used in solid-statefermentation.

Tabla 1. Tamano de salvado de arroz utilizado en lafermentacion en estado solido.

Granulometry Mass (g)* Yield (%)

Ty 14 (1.18 mm) 8.7 + 0.63 8.7Ty 24 (0.71 mm) 23.7 + 0.63 23.7Ty 28 (0.6 mm) 9.3 + 0.43 9.3Ty 32 (0.5 mm) 3.3 + 0.49 3.3Ty 35 (0.425 mm) 6.3 + 0.49 6.3Ty 42 (0.355 mm) 5.7 + 0.5 5.7Bottom 41.6 + 1.0 41.6Total 98.6 + 2.0

Note: *The results are expressed as Means + SD.

Nota: *Los resultados se expresan como Medios + SD.

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mycotoxins contamination levels in 80% and increasedprotein content in 17%. Silveira and Badiale-Furlong(2007) verified that the action of Rhizopus spp.increased protein, digestible amino acids and availablemethionine content in rice bran.

There was a temperature increase during thefermentation process, probably because of moistureloss observed in Table 2, despite the moisture excess inthe fermentation chamber. Statistical analysis indicatedthat the fermented bran did not differ in free watercontent along the time.

The ash content of rice bran was similar to theresults found by other authors which were 11.7%,10.5%, and 10% (Feddern, Badiale-Furlong, & Souza-Soares, 2007; Oduguwa, Edema, & Ayeni, 2008;Silveira & Badiale-Furlong, 2007). There was asignificant increase in fermented rice bran ash contentfrom 48 h on; this result is probably due to fungusinherent ash content. The increase in ash contentreached 30% in 120 h. Similar phenomenon wasobserved by Oduguwa et al. (2008) in relation toRhizopus oligosporus and Saccharomyces cerevisiae,using rice bran as substrate, they found an increase of24.5% after 48 h of fermentation in ash content. Thefungi ash content can vary between 1% and 29%,depending on species and growth conditions (Griffin,1994). According to Chaud and Sgarbieri (2006), thecell wall of Saccharomyces cerevisiae presents 1.4%ash, 2% of total lipids and 3.8% insoluble fiber.

The bran fiber content fermented for 120 h showeda 60% significant increase comparing to time zero. Thisfiber increase comes from the intrinsic chitin produc-tion of R. oryzae. The fungi produce several poly-saccharides; some are similar to other sourcesstructures. These compounds may be exocellularassociated with the membrane and cell wall or theycan be intracellular. The fungi polysaccharides arecommonly cellulose and chitin (Griffin, 1994). Yoon,Nam, and Kang (2008) obtained more than 100%

increase in dietary fiber content in fermented rice branwith ethanolic extracts by four different fungi.

The mycelia of various fungi including Absidiacoerulea, Absidia glauca, Aspergillus niger, Colletotri-chum lindemuthianum, Gangronella butleri, M. rouxii,Phycomyces blakesleeanus, Pleurotus sajo-caju, R.oryzae, Lentinus edodes, and Trichoderma reesei hasbeen suggested as alternative sources of chitosan(Suntornsuk, Pochanavanich, & Suntornsuk, 2002;Wu, Zivanovic, Draughon, & Sams, 2004).

The rice bran lipid content was 18.9% in agreementwith values obtained by other authors (Amissah, Ellis,Oduro, & Manful, 2003; Silva, Sanches, & Amante,2006). The results determined that the unfermentedand fermented brans until 24 h were not statisticallydifferent at a 5% level. The reduction of lipidcontent from 48 h on was significantly different fromthe first ones; these results are due to lipid use by thefungus for chitin synthesis. Oduguwa et al. (2008)reported a 40% reduction in fat content in rice branfermented by R. oligosporus and Saccharomycescerevisiae.

The phytic acid is the primary storage compound ofphosphorus (80% of total) in seeds, accounting for1.5% of its dry weight. The undesirable change ofphosphate to phytic acid, attached to metal cations ofCa, Fe, K, Mg, Mn and Zn make them insoluble andunavailable as nutritional factors. The phytates accu-mulate mainly in vacuoles of storage proteins, pre-dominantly located in the aleurone layer (wheat, rice,and barley) or germ (embryo-corn). During germina-tion, phytate is hydrolyzed by the endogenous phytasesand other phosphatases to release phosphate, inositol,and micronutrients for plant growth support (Bohn,Meyer, & Rasmussen, 2008). The phytates have severalimportant physiological functions in the plant duringits life cycle, including storage of cations and phos-phorus, providing material for the formation of cellwalls, after the germination of seeds. Furthermore, the

Table 2. Physico-chemical composition of fermented and unfermented rice bran.

Tabla 2. Composicion fısico-quımica del salvado de arroz fermentado y sin fermentar.

Rice bran Moisture (g kg71) Ash (g kg71) Fiber (g kg71) Fat (g kg71)Reducing sugars(mgglucose g

71db) Phytic acid (g kg71)

NF 118 + 0.05a 104 + 1.1ab 85 + 0.3a 189 + 0.2a 21.0 + 2.7a 10 + 0.03a

0 h 479 + 0.2b 93 + 0.05a 81 + 0.2a 204 + 1.2a 22.0 + 0.2a 9.0 + 0.03b

24 h 463 + 0.3b 114 + 0.20b 110 + 0.1b 195 + 0.5a 47.6 + 0.5b 3.0 + 0.02c

48 h 421 + 2.1b 135 + 0.44c 128 + 0.03c 159 + 0.2b 13.2 + 0.3c 4.0 + 0.02d

72 h 425 + 7.3b 133 + 0.11c 126 + 0.3bc 131 + 0.4c 8.5 + 0.3d 4.0 + 0.03d

96 h 404 + 2.2b 141 + 0.10c 145 + 0.5d 110 + 0.1c 7.7 + 0.4d 4.0 + 0.02d

120 h 361 + 3.5b 136 + 0.14c 131 + 0.8cd 112 + 0.5c 7.9 + 0.1d 4.0 + 0,03d

Notes: The values in each column with the same overwritten letter are not significantly different (p 5 0.05).

Values are expressed as Means + SD.

NF, bran not fermented; bran fermented for 0 h, 24 h, 48 h, 72 h, 96 h and 120 h.

Notas: Los valores en cada columna con el mismo superındice no son significativamente diferente (p 5 0,05).Los valores se expresan como Medios + SD.NF, salvado no fermentado; salvado fermentado durante 0 h, 24 h, 48 h, 72 h, 96h y 120 h.

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phytic acid would protect the seed against oxidativedamage during storage.

Phytases are phosphohydrolases which begin thephosphate removal stage from phytate. These enzymesare used in feed to improve the nutrition of phosphorusto reduce its pollution from animal waste. Thepotential of phytases in improving human nutritionin trace mineral elements coming from foods ofvegetable sources is being explored (Lei & Porres,2003). The phytic acid content in rice bran was 10 gkg71, expected to occur in rice, which has a range from1 to 5% of the total grain weight. The phytic acidextraction method used in this study showed recoveryof 84% and variation coefficient of 9%.

After 24 h of fermentation the phytic acid contentdecreased significantly, 66–55%, in relation to thebeginning of the fermentation, resulting in fungiphytase production. Some species of Rhizopus spp. asR. oryzae, R. oligosporus, and R. ostolonifer and somespecies of Aspergillus are listed as phytase producers(Ramachandran et al., 2005). Kadan and Phillippy(2007) determined the content of phytates in rice breadcontaining defatted rice bran and different amounts ofyeast. The researchers observed a degradation ofphytates by 42% when the product contained 3.7%of rice bran after bread fermentation, regardless of theamount of yeast.

Figure 1 shows the performance of reducing sugarscontent during fermentation. In 24 h there was anincrease of these compounds, but as the time passed thereducing sugar content decreased significantly from48 h to 120 h. The results showed the fungus ability inhydrolyzing the substrate carbohydrates to glucose,which is for its own use. Similar behavior was found byother authors (Alam et al., 2009; Gelinas & Barrete,2007). The effect of fermentation can be exploited evenon vitamins, minerals, amino acid profile and othercompounds, complementing the studies to enable therecovery and use of these formed compounds.

Knowledge of the fermentation agent compositionhelps elucidate the changes in raw material.

The bioconversion of agroindustrial raw materialsis a potential for protein production, especially for feednutritional supplementation. These products are alsosources of high added value compounds such asenzymes, vitamins, amino acids, antioxidants, andminerals (Ghorai et al., 2009). Some fungi arereferenced in various studies by helping to increasethe protein content of different agroindustrial rawmaterials (Anupama & Ravindra, 2000; Gelinas &Barrete, 2007; Oduguwa et al., 2008).

Table 3 presents fermented and unfermented ricebran results of protein levels and digestible aminoacids.

The values for unfermented bran are in agreementwith the literature (Feddern et al., 2007; Pestana,Mendonca, & Zambiazi, 2008; Silva, Sanches, &Amante,

Table 3. Biomass protein content, percentage of protein increase and digestible amino acids.

Tabla 3. Contenido de proteınas, porcentaje de aumento de proteına y aminoacidos digeribles de la biomasa.

Fermentation time Protein (g kg71)Increase in

protein content (%)Digestible AA(mg gmedium

71)Digestible AA(mg g protein

71)

NF 147 + 0.7a 11.0 + 0.29a 74.9 + 2.0a

0 h 164 + 0.17b 11.9 + 0.38a 72.7 + 2.3a

24 h 210 + 0.15c 28.2 20.1 + 0.38b 95.7 + 1.8b

48 h 220 + 0.1cd 34.6 19.9 + 0.44bc 90.4 + 1.9bc

72 h 230 + 0.5de 40.6 18.7 + 0.11cd 81.2 + 0.5a

96 h 234 + 0.5e 42.8 19.8 + 0.31bd 84.7 + 1.3ac

120 h 230 + 0.4de 38.6 20.4 + 0.43b 88.9 + 1.8bc

Notes: The values in each column with the same overwritten letter are not significantly different (p 5 0.05).Values are expressed Means + SD (n ¼ 3).NF, bran not fermented; bran fermented for 0 h, 24 h, 48 h, 72 h, 96 h and 120 h; AA, amino acid.

Notas: Los valores en cada columna con el mismo superındice no son significativamente diferentes (p 5 0.05).Los valores se expresan como Medios + SD (n ¼ 3).NF, salvado no fermentado; salvado fermentado durante 0 h, 24 h, 48 h, 72 h, 96 h y 120 h; AA, aminoacido.

Figure 1. Reducing sugars content in rice bran fermentedby Rhizopus oryzae.

Figura 1. Contenido de azucares reductores en el salvado dearroz fermentado con Rhizopus oryzae.

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2001). The development of fungal biomass resulted in afermented bran protein content increase which wassignificantly different, comparing the protein valuesfrom 24 h on in relation to the beginning of the process.This increase reached 42.8% after 96 h of fermentationcompared to the beginning. However, it can be noted thatwithin 24 h there was an increase of 4.6 percentage pointsin relation to the beginning of the fermentation time andin 48 h the increase was one percentage point over thesame interval, keeping this behavior for 72 h anddecreasing at 96 h and 120 h. These results indicatethat in the first 24 h of the fermentation process the fungiare in full metabolic activity.

Rudravaram, Chandel, Linga, and Pogaku (2006)studied protein enrichment of deoiled rice bran bysolid-state fermentation using Aspergillus oryzae. Theyachieved the maximum protein enrichment (100%) in 3days, while the yield achieved in the present work in thesame period was 34.6% using whole rice bran.However, fermented rice bran application on animalfeed or food may contribute to increase the nutritionalquality of the product, once its lipid content is richin antioxidant compounds and unsaturated fattyacids. Lee, Hong, and Cho (2008), mentioned thatfermented rice bran can be source of compounds withantibacterial and antioxidant activity, besides present-ing tyrosinase inhibition. Kim et al. (2002) reportedthat mice administered with hot water extract offermented rice bran showed anti-stress and anti-fatigueeffects.

Due to the significant increase in protein content ofthe biomass, the quality of this produced compound

was the target of interest. So the content of amino acidswas estimated after a process of enzymatic digestion.The determined digest amino acids, when expressed onmass of fermented bran, had increased*50% from the24 h and were maintained throughout the experiment.This result in relation to protein bran showed that thedigested amino acids increased from 18.5% to 27.6%,indicating an increase in digestibility of the biomass onthe non-fermented rice bran.

Figure 2 shows the original protein content of thebran and the contents of digested protein andsolubilized after the process of digestion, measuredand quantified by an albumin standard curve. Theresults showed an increased content of soluble proteinsduring fermentation. This component can be thesubject to further studies to verify its quality.

Conclusion

The results of this study showed that the fermentationprocess caused changes in the physico-chemical com-position of fermented rice bran in solid medium by R.oryzae. The fermentation caused a reduction of 24.6%,40%, and 50% in moisture, lipids and phytic acid inbran, respectively. The reducing sugars were 60%consumed during fermentation. The fermented branhad higher content of ash, fiber and protein, with anincrease of 30%, 50%, and 40%, respectively. Thelevels of digestible amino acids showed an increase of27.6% in the digestibility of the produced proteins.

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Figura 2. Comparacion del contenido de proteınas delsalvado de arroz y de la biomasa, proteına digerible e solubledespues del proceso de digestion enzimatica.

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