Statistical Optimization of Dilute Acid Hydrolysis of Wood Sawdust for Lactic Acid Production

Abstract

Abbreviations: SW, sawdust wood; CCD, central composite design; LAB, lactic acid bacteria; L-LDH, L-lactate dehydrogenase; RSM, response surface methodology; 3D, 3-dimensional; MSW, meranti wood sawdust; OFI, Opuntia ficus indica IntroductionLactic acid has a wide application in food, pharmaceutical, leather, cosmetic applications, textile, and polylactic acid industries.1-3 Lactic acid can be produced either by fermentation or by chemical synthesis. But the biotechnological fermentation process has received significant importance due to environmental concerns, use of renewable resources instead of petrochemicals, low production temperature, low energy requirements, and high purity. Mammalian cells only contain L-lactate dehydrogenase (L-LDH), so L(+) form of lactic acid is used for food and drug industry, because the human body is only adapted to assimilate this form by the action of the enzyme L-LDH whereas D-lactic acid is often harmful to human metabolism, his accumulation in the blood can cause acidosis. 4,5 Lactic acid can be synthesized by microbial fermentation of the various raw materials such as molasses, 6 whey, 7 and date juice. 8 As in any industrial organic acid or solvent fermentation, the main economic factors are the choice and cost of the substrate and the cost of recovery in downstream processing. Feedstock that would reduce the processing cost would greatly enhance the competitiveness of fermentative lactate production. Many efforts have been made to develop biotechnologies for lactate generation from such a cheap, abundant and renewable substrate. Recently, fermentation of non-food biomass has also gained considerable attention due to the forthcoming scarcity of fossil fuels and the increased lack of food and feed supplies over the world. Biomass of lignocelluloses is a low-cost and extensively available renewable carbon source as an alternative to the conventional feed stocks.9-11 Lignocellulosic biomass is primarily composed of cellulose, hemicellulose, and lignin. 12,13 A cellulosic feedstock (such as wood) has been widely used to replace refined sugar, and been utilized for the production of ethanol, 14,15 single cell protein, 16 xylitol 17 and organic acid such as lactic acid. 18The conversion of wood to lactic acid is more challenging due to the complex structure of the lingocellulose. The three polymers of Lignocellulosic biomass are arranged to form a highly recalcitrant structure, 19 hindering the availability of carbohydrates for fermentation processes, representing a high barrier for the bioconversion of lignocellulosic material. In fact it is necessary to pretreat the wood to alter its structural and chemical composition to facilitate hydrolysis of carbohydrates to fermentable sugars. 20,21 Pretreatment uses various techniques, including ammonia fiber explosion, chemical treatment, biological treatment, and steam explosion, to alter the structure of cellulosic biomass to make cellulose more accessible. Conversion of wood lignocellulosic biomass to glucose and other monomeric suga...

Production of Lactic Acid from Seaweed Hydrolysates via Lactic Acid Bacteria Fermentation

“…There have been a number of reports describing the strategy of using a combination of dilute acid/alkaline pretreatment and enzymatic hydrolysis for cellulosic biomass saccharification [43,44,46,47]. Alkaline pretreatment and enzymatic hydrolysis of wheat straw (50 g/L) can generate a reducing sugar of 13.82 g/L [43], and dilute acid hydrolysis followed by enzymatic hydrolysis for wood sawdust could generate glucose at 8.68 g/L [48]. However, few studies have reported the saccharification of marine algae.…”

Multi-response and multi-criteria optimization of acid hydrolyzate detoxification of cocoa pod husks: Effect on the content of phenolic compounds and fermentable sugars

“…By default, the high levels of the factors are coded +1, and the low levels are coded −1. Plus Signs (+) represent a synergistic relationship, while minus signs (−) indicate antagonism between variables [ 27 ]. The quadratic equations obtained by regression analysis are presented in equations (3) , (4) ), for the content of PC and RS.…”

“…This is perceived through the arrangement of the points grouped around the regression line. In addition, since least-squares residuals are an important tool for judging the fit of the model [ 27 ], Fig. 3 , Fig.…”