Bioconversion from crude glycerin by Xanthomonas campestris 2103: xanthan production and characterization

Abstract

-The production and rheological properties of xanthan gum from crude glycerin fermentation, a primary by-product of the biodiesel industry with environmental and health risks, were evaluated. Batch fermentations (28 °C/250 rpm /120 h) were carried out using crude glycerin, 0.01% urea and 0.1% KH 2 PO 4 , (% w/v), and compared to a sucrose control under the same operational conditions, using Xanthomonas campestris strain 2103 isolate from Brazil. Its maximal production by crude glycerin fermentation was 7.23±0.1 g·L -1 at 120 h, with an apparent viscosity of 642.57 mPa·s, (2 % w/v, 25 °C, 25 s -1 ), 70% and 30% higher than from sucrose fermentation, respectively. Its molecular weight varied from 28.2 to 36.2×10 6 Da. The Ostwald-de-Waele model parameters (K and n) indicated a pseudoplastic behavior at all concentrations (0.5 to 2.0 %, w/v) and temperatures (25-85 °C), while its consistency index indicated promising rheological properties for drilling fluid applications. Therefore, crude glycerin has potential as a cost-effective and alternative substrate for non-food grade xanthan production.

Glycerol as a carbon source for xantan production by Xanthomonas campestris isolates

“…The yields range between 7.24 g/L for ATCC 13951 and 1.68 g/L for the isolate I5. The highest yield values are slightly higher than the values listed in the literature (11). From an economical point of view, when glycerol is used as a sole carbon source the obtained yield values are low, but the mere possibility of using this alternative carbon source in the biotechnological production of xanthan is very significant.…”

“…The medium used for the inoculum preparation was YM ® broth, while xanthan production was performed on the media containing glucose or glycerol (Table 1). Literature data (11) were used for the formulation of the cultivation medium based on glycerol. The pH value of the medium was adjusted to 7.0±0.2 and then sterilized by autoclaving under standard conditions.…”

“…If xanthan would be produced on a medium with a low-cost carbon source, production costs would decrease (8), which is why numerous waste effluents have been suggested as alternative carbon sources (2,9). Glycerol, the main by-product of the biodiesel production process, is one such cheap and available substrate used for the biotechnological production of various products, one of which is xanthan (10,11).…”

Xanthan gum production by <i>Xanthomonas axonopodis pv. mangiferaeindicae</i> from glycerin of biodiesel in different media and addition of glucose

“…In the present study, the gum concentration obtained at the best condition (3.2 kg m -3 ) is in good agreement with the literature. Brandão et al (2013) used the same strain of the present study to produce xanthan gum from glycerin of biodiesel in a peptone and extracts free medium. They observed a cell concentration of 5 kg m -3 and 7 kg m -3 xanthan at the end of 120 hours cultivation.…”

“…Glucose is usually the most widely used carbon source in the production of xanthan gum (Rosalam & England, 2005), but other sources have been successfully studied to substitute and cheapen the process, such as whey (Nitschke, Rodrigues, & Schinatto, 2001), apple juice residue (Druzian & Pagliarini, 2007), soluble compounds of the green coconut shell (Nery, Cruz, & Druzian, 2013), cassava whey (Brandão, Esperidião, & Druzian, 2010), sugarcane juice (Brandão, Nery, Machado, Esperidião, & Druzian, 2008), lignocellulosic agro-industrial wastes (Silva et al, 2018) and glycerin from biodiesel (Brandão et al, 2013). Since glycerin is low in cost and represents an environmental problem, it is a good option, but further research is needed to determine optimum growth conditions.…”