Feasibility of exhausted sugar beet pulp as raw material for lactic acid production

Abstract

BACKGROUND Exhausted sugar beet pulp pellets (ESBPP), a sugar industry by‐product generated after sugar extraction in the sugar production process, have been used as a raw material for lactic acid (LA) production via hydrolysis and fermentation by Lactobacillus casei. To design a more cost‐effective process, simultaneous saccharification and fermentation (SSF) of ESBPP is proposed in the present study. The effects of pH control, nutrient supplementation and solid addition in fed‐batch SSF on lactic acid production were investigated. RESULTS The highest LA concentration (26.88 g L–1) was reached in fed‐batch SSF at a solid/liquid loading of 0.2 g mL–1, with pH control (by adding 30 g L–1 CaCO3 to the medium) and nutrient supplementation (by adding 20 mL of MRS medium per 100 mL of buffer). Under these conditions, a maximum productivity of 0.63 g L−1 h−1 was achieved, which is 2.7 times higher than that attained in the control experiment (SSF inoculated at time 0 h). However, a slightly lower LA yield was obtained, revealing the need of an increasing dose of enzymes at high solid loading SSF. CONCLUSION An efficient fed‐batch SSF strategy with pH control and MRS supplementation is described in the present study, attaining higher LA productivity compared to separate hydrolysis and fermentation and SSF. © 2020 Society of Chemical Industry

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

“…The other bacterium used in this work was L. casei (2246), which is also considered to be a facultative heterofermentative one. This strain was tested in a previous study obtaining, as for the other strain under study, that it could metabolise only glucose and arabinose among all the sugars tested 20 …”

“…The growth of L. plantarum was tested in three MRS mediums with different carbon sources (glucose, xylose or arabinose). The same test was performed using L. casei in a previously published work 20 . Fermentations were carried out in 250 mL Erlenmeyer flasks by adding 50 mL of the synthetic medium supplemented with the neutralising agent CaCO 3 (9 g L −1 ) and 0.5 mL of inoculum ( ca 10 9 cells mL −1 ).…”

Sugar Beet Pulp as Raw Material for the Production of Bioplastics

“…They increased the production of LA to 50 g/L with a yield of 0.5 g LA /g SBP when the SBP was pretreated with 1% H 2 SO 4 [52]. Díaz et al studied different simultaneous saccharification and fermentation strategies to produce LA from SBP with Lactobacillus casei [95]. They achieved the maximum concentration of 27 g/L of LA with a yield of 0.13 g LA /g SBP using a fed-batch SSF process with pH control (by adding 30 g/L CaCO 3 ) and nutrient supplementation (by adding MRS medium 0.2 mL/mL).…”

“…They achieved the maximum concentration of 27 g/L of LA with a yield of 0.13 g LA /g SBP using a fed-batch SSF process with pH control (by adding 30 g/L CaCO 3 ) and nutrient supplementation (by adding MRS medium 0.2 mL/mL). Lactobacillus plantarum SHF 30 g/L 0.12 g/g [52] Lactobacillus plantarum SHF with pretreated SBP 50 g/L 0.5 g/g [95] Lactobacillus casei Fed-fach SSF 27 g/L 0.13 g/g [97] Bacillus coagulans Continuous fermentation 35 g/L 0.71 g/g…”

“…However, pentoses are only utilized by some lactobacilli. This is the case of the facultative heterofermentative microorganism Lactobacillus casei 2246, which degrades hexoses, mainly glucose, through the EMP pathway, and pentoses by the PK pathway [95]. This strain has been demonstrated to produce lactic acid from glucose and arabinose from simultaneous saccharification and fermentation of SBP.…”