Valorisation of fungal hydrolysates of exhausted sugar beet pulp for lactic acid production

Abstract

BACKGROUND Exhausted sugar beet pulp pellets (ESBPP) were used as raw material for lactic acid (LA) fermentation. The enzymatic hydrolysis of ESBPP was performed with the solid obtained after the fungal solid‐state fermentation of ESBPP as a source of hydrolytic enzymes. Subsequently, a medium rich in glucose and arabinose was obtained, which was used to produce LA by fermentation. For LA production, two Lactobacillus strains were assayed and the effects of the supplementation of the hydrolysate with a nitrogen source and the mode of pH regulation of the fermentation were investigated. Moreover, a kinetic model for LA fermentation by Lactobacillus plantarum of ESBPP hydrolysates was developed. RESULTS L. plantarum produced a LA concentration 34% higher than that produced by L. casei. The highest LA concentration (30 g L−1) was obtained with L. plantarum when the hydrolysate was supplemented with 5 g L−1 yeast extract and the pH was controlled with CaCO3. The concentration of acetic acid differed depending on the concentration of CaCO3 added, producing its maximum value with 27 g L−1 CaCO3. The proposed kinetic model was able to predict the evolution of substrates and products depending on the variation of the pH in the hydrolysate, according to the amount of CaCO3 added. CONCLUSIONS ESBPP can be revalorised to produce LA. A pure LA stream or a mixture of LA and acetic acid, depending on the pH control method of the fermentation, can be produced. Thus, this control is of great interest depending on the destination of the effluent. © 2020 Society of Chemical Industry

Effect of Several Pretreatments on the Lactic Acid Production from Exhausted Sugar Beet Pulp

“…Almost complete removal of the hemicellulose fraction, with low cellulose solubilisation, was reached with 2.5% w/v of H 2 SO 4 at 150 • C for 30 min [33]. As in our study, Canilha et al observed the lowest solid solubilization when it was pretreated in absence of acid, confirming that an acid catalyst is necessary to degrade hemicellulose at moderate temperatures [33,36].…”

Sugar Beet Pulp as Raw Material for the Production of Bioplastics

“…To increase the LA yield, several authors have varied the pH regulation mode, nutrient supplementation and the type of processing, such as separate hydrolysis and fermentation, simultaneous saccharification and fermentation, fed-batch fermentation or continuous fermentation. For instance, Marzo et al studied the effect of supplementing the SBP hydrolysate with different nitrogen sources, finding that it is necessary to supplement it with yeast extract to increase the production of LA [94]. Additionally, they also studied pH regulation during the lactic fermentation of SBP hydrolysate with Lactobacillus plantarum, reaching 30 g/L of LA with a yield of 0.12 g LA /g SBP by adding 27 g/L of CaCO 3 [94].…”

“…For instance, Marzo et al studied the effect of supplementing the SBP hydrolysate with different nitrogen sources, finding that it is necessary to supplement it with yeast extract to increase the production of LA [94]. Additionally, they also studied pH regulation during the lactic fermentation of SBP hydrolysate with Lactobacillus plantarum, reaching 30 g/L of LA with a yield of 0.12 g LA /g SBP by adding 27 g/L of CaCO 3 [94]. In another report, the same authors evaluated the pretreatment of SBP, testing acid, alkaline and biological pretreatment.…”