No abstract

Biopolímeros são polissacarídeos de origem microbiana, sintetizados por bactérias, fungos e leveduras. Xantanas são exopolissacarídeos (EPS), que possuem a capacidade de formar géis e soluções viscosas em meio aquoso (MEDEIROS et al. 2000). Apresentam-se como uma alternativa às gomas tradicionais devido às suas propriedades reológicas, sendo amplamente utilizadas como espessantes, geleificantes, agentes de suspensão, colóides protetores e estabilizantes, nas indústrias de alimentos, farmacêutica, química e petroquímica (FARIA, 2005;LIMA et al., 2001).A goma xantana é um biopolímero classificado como heteroexopolissacarídeo ramificado, aniônico, produzido por fermentação, empregando a bactéria Xanthomonas campestris.Essas bactérias apresentam células em forma de bastonetes, Gram-negativas e ocorrem predominantemente isoladas .Os polissacarídeos extracelulares apresentam maior interesse industrial, devido à maior facilidade de extração e purificação, e por não sofrerem influências sazonais (MARCOTTE; TAHERIAN;RAMASWAMY, 2001). Segundo Foresti (2003), atualmente a xantana é o polissacarídeo com maior estabilidade entre os existentes no mercado, por formar soluções aquosas de alta viscosidade, extremamente pseudoplásticas. A viscosidade, que pode ser tomada como parâmetro de qualidade, é influenciada pelo tipo das cepas, composição do meio de fermentação e pelas condições operacionais utilizadas na produção. AbstractThe xanthan gum is a heteroexopolysaccharide synthesized by Xanthomonas campestris in a culture medium using glucose or sucrose as carbon sources and other nutrients. Due to its rheological properties, it has been contributing for the range of applications in the food industry, pharmaceutical, and tertiary recovery of oil. Sugarcane is rich in nutrients (sugars and minerals) and can be used as a substratum for the xanthan production, which can be produced in Brazil due to its cost reduction. The objective of this study was to test the production of the xantana obtained with different culture native of Xanthomonas in medium composed of sugarcane broth (XSC) and to compare with the values obtained with sucrose (XS). Two medium cultures were used with the minimum of the nutrients, contained sucrose or sugar cane complemented with urea (0.01%) and K 2 HPO 4 (0.1%), fermented in shaker (28 °C, 250 rpm, 120 hours). The best production was obtained using Xanthomonas campetris manihotis and sugarcane (33.54 g.L -1 ), approximately ten times bigger then obtained with the sucrose (3.45 g.L -1 ). The apparent viscosity for an aqueous solution of 2.0% of gum to 25 °C and 25 s -1 was 99.36 mPa.s for XSC and 500.43 mPa.s to XS. The biosynthesis of xanthan starting from sugarcane deserves peculiar attention, constituting like this, a promising possibility for gum production in wide climbs. Keywords: xanthan gum; biopolymer; sugarcane; Xanthomonas campestris. ResumoGoma xantana é um heteroexopolissacarídeo sintetizado por Xanthomonas utilizando glicose ou sacarose como fontes de carbono, além de outros micronutrientes....

Interest in nanocellulose obtained from natural resources has grown, mainly due to the characteristics that these materials provide when incorporated in biodegradable films as an alternative for the improvement of the properties of nanocomposites. The main purpose of this work was to investigate the effect of the incorporation of nanocellulose obtained from different fibers (corncob, corn husk, coconut shell, and wheat bran) into the chitosan/glycerol films. The nanocellulose were obtained through acid hydrolysis. The properties of the different nanobiocomposites were comparatively evaluated, including their barrier and mechanical properties. The nanocrystals obtained for coconut shell (CS), corn husk (CH), and corncob (CC) presented a length / diameter ratio of 40.18, 40.86, and 32.19, respectively. Wheat bran (WB) was not considered an interesting source of nanocrystals, which may be justified due to the low percentage of cellulose. Significant differences were observed in the properties of the films studied. The water activity varied from 0.601 (WB Film) to 0.658 (CH Film) and the moisture content from 15.13 (CS Film) to 20.86 (WB Film). The highest values for tensile strength were presented for CC (11.43 MPa) and CS (11.38 MPa) films, and this propriety was significantly increased by nanocellulose addition. The results showed that the source of the nanocrystal determined the properties of the chitosan/glycerol films.

Xanthan, a biopolymer with extensive industrial applications, is commercially produced by fermenting glucose or sucrose using the bacteria Xanthomonas. Green coconut shells, rich in nutrients, could be an alternative substrate to obtain xanthan. This study aimed to evaluate the production and rheological properties of xanthan obtained on different fermentation scales using green coconut shells as the substrate, using its production from sucrose for comparison. Media containing minimal nutritional requirements (carbon, urea, phosphate) were prepared. Upon changing from the conventional medium to the alternative medium there was a 30% increase in production using the shaker and 81% increase using the bioreactor. Increasing the fermentation scale resulted in an increased yield of xanthan and a 30% increase in apparent viscosity. Coconut shells deserve special attention, constituting a possibility for the large scale production of xanthan with cost reduction and application of a residue.