Environmentally Friendly Production of D(−) Lactic Acid by Sporolactobacillus nakayamae: Investigation of Fermentation Parameters and Fed-Batch Strategies

Abstract

The interest in the production of lactic acid has increased due to its wide range of applications. In the present study, the variables that affect fermentative D(−) lactic acid production were investigated: neutralizing agents, pH, temperature, inoculum percentage, agitation, and concentration of the medium components. An experimental design was applied to determine the optimal concentrations of the medium components and fermentation was studied using different feeding strategies. High production (122.41 g/L) and productivity (3.65 g/L·h) were efficiently achieved by Sporolactobacillus nakayamae in 54 h using a multipulse fed-batch technique with an initial medium containing 35 g/L of yeast extract (byproduct of alcohol production), 60 g/L of crystallized sugar, and 7.5 mL/L of salts. The fermentation process was conducted at 35°C and pH 6.0 controlled by NaOH with a 20% volume of inoculum and agitation at 125 rpm. The production of a high optically pure concentration of D(−) lactic acid combined with an environmentally friendly NaOH-based process demonstrates that S. nakayamae is a promising strain for D(−) lactic acid production.

Production of L (+) Lactic Acid by Lactobacillus casei Ke11: Fed Batch Fermentation Strategies

“…Figure 2c shows that the ideal concentration for greater lactic acid production was between 30 and 50 g/L of yeast extract and the ideal percentage of inoculum was between 10 and 20%. Beitel et al [19] found that maximum lactic acid production (113.73 g/L) and a low concentration of residual sucrose (3.37 g/L) were obtained when 20% (v/v) inoculum was used in the culture medium. However, a lower concentration of lactic acid was obtained (82.34 g/L) using 5% (v/v) inoculum, which may be attributed to the low density of the inoculum.…”

“…High performance liquid chromatography of the fermented broth was used for the quantification and determination of L(+)lactic acid according to Beitel et al [19], using a column Rezex ROA 300 mm × 7.8 mm (phenomenex, Burlington, MA, USA) and differential refracting index detector (Shimadzu Ultra Fast Liquid Chromatograph, Kyoto, Japan ). The mobile phase (0.005 M H 2 SO 4 ) was fed at a flow rate of 0.6 mL/min, and the temperature was kept 65 • C, and Chirex 2126 Phenomenex (150.00 × 4.60 mm) column with 1 mM of CuSO 4 as the mobile phase at 1 mL/min and temperature of 26 • C, respectively.…”

“…Lai et al [64] compared the performance of the batch mode and fed batch mode and found that the latter led to a higher concentration of lactic acid, yield and productivity. The fed batch mode can increase the content of the final product in the bioreactor, maintaining a low concentration of substrate during fermentation and thereby avoiding the inhibitory effect of the sugar and reducing the effect of osmotic pressure on the bacterial cells [19].…”

“…gardening residues [17], crystal sugar [18,19], municipal biopulp [20], Kodo millet bran hydrolysate [21,22], bakery waste and lucerne green juice [23], sugarcane bagasse [24][25][26] and sugar beet pulp [27].…”

“…Sugar in its pure form (sucrose, lactose and glucose) is the preferred carbon source. Despite being an expensive raw material, these sugars ensure a high yield and reduce the cost of purification [18,19,33]. Nitrogen sources also constitute a factor correlated with the production of lactic acid, as LAB require complex media [34].…”