Comparison of high-titer lactic acid fermentation from NaOH- and NH3-H2O2-pretreated corncob by Bacillus coagulans using simultaneous saccharification and fermentation

Abstract

Lignocellulose is one of the most abundant renewable feedstocks that has attracted considerable attention as a substrate for biofuel and biochemical production. One such biochemical product, lactic acid, is an important fermentation product because of its great potential for the production of biodegradable and biocompatible polylactic acid. High-titer lactic acid production from lignocellulosic materials has been achieved recently; however, it requires biodetoxification or results in large amounts of waste washing water. In this study, we employed two alkaline pretreatment methods and compared their effects on lactic acid fermentation of pretreated corncob by Bacillus coagulans LA204 using fed-batch simultaneous saccharification and fermentation under non-sterile conditions. The lactic acid titer, yield, and productivity from 16% (w/w) NaOH-pretreated and washed corncob were 122.99 g/L, 0.77 g/g corncob, and 1.37 g/L/h, respectively, and from 16% NH3-H2O2-pretreated and washed corncob were 118.60 g/L, 0.74 g/g corncob, and 1.32 g/L/h, respectively. Importantly, the lactic acid titer, yield, and productivity from 18.4% NH3-H2O2-pretreated and unwashed corncob by using fed-batch simultaneous saccharification and fermentation reached 79.47 g/L, 0.43 g/g corncob, and 1.10 g/L/h, respectively, demonstrating that this method is possible for industrial applications and saves washing water.

Biodetoxification of Phenolic Inhibitors from Lignocellulose Pretreatment using Kurthia huakuii LAM0618T and Subsequent Lactic Acid Fermentation

“…In addition to phenolic inhibitors, formate and acetate, which act as fermentation inhibitors, are also generated by alkaline pretreatment of a lignocellulosic biomass [ 9 ]. The growth of K. huakuii LAM0618 T and degradation of formate and acetate were tested in YPD medium (pH 6.0) containing different concentrations (2.0, 4.0, 6.0, and 8.0 g/L) of these inhibitors.…”

“…Dilute acid, dilute alkaline, and alkaline peroxide pretreatments were compared, with wheat straw and corncob as substrates. These comparisons revealed that the alkaline peroxide pretreatment is the most appropriate method for ethanol and lactic acid production even without rinsing of the pretreated substrates [ 8 , 9 ]. In addition, the alkaline peroxide pretreatment retained more of the hemicellulose than during other pretreatments, and dissolved a portion of the lignin, promoting enzymatic hydrolysis and reducing the inhibitory effect of lignin derivatives on subsequent fermentation [ 8 ].…”

“…Although chemical pretreatments are a simple and efficient way of pretreating lignocellulosic materials, these pretreatments inevitably generate several types of soluble inhibitors, such as furan derivatives (furfural and hydroxymethylfurfural [HMF]), generated during dilute acid pretreatments; and phenolic compounds as well as formate and acetate, generated by alkaline pretreatments [ 8 , 9 , 10 ]. For example, 2~5 g/L total phenolic inhibitors was detected in the lactic acid fermentation cultures using NH 3 /H 2 O 2 -pretreated corncob as substrate [ 9 ]. These compounds inhibit microbial activity and enzyme hydrolysis, which in turn hinders the industrial production of biofuels and biochemicals [ 11 , 12 , 13 ].…”

Enhanced lactic acid production by Bacillus coagulans through simultaneous saccharification, biodetoxification, and fermentation

“…Corncob (LianFeng Processing of Agricultural Products Co. Ltd, Lianyungang, China) was cleaned, dried, and sieved using a 0.15 mm mesh. The corncob was then pretreated using the NH 3 ‐H 2 O 2 system, as we reported previously . Briefly, 1000 g of corn stover was pretreated with 3% NH 3 ·H 2 O for 2 days, and then pretreated with 5% H 2 O 2 for 7 days at room temperature.…”

Supercritical Fluids: A Promising Technique for Biomass Pretreatment and Fractionation

“…Several pretreatment techniques have been studied to improve the conversion of lignocellulosic materials into sustainable fuels, value-added chemicals and functional materials (Rajan and Carrier, 2014;Zhang et al, 2016;Qi et al, 2017). Pretreatment normally enhances substrate accessibility by breaking down the hemicellulose and/or lignin interface and expose the cellulose matrix to the concerted action of cellulolytic enzymes (Mood et al, 2013).…”