Production of D-lactic acid from defatted rice bran by simultaneous saccharification and fermentation

Biological production of functional chemicals from renewable resources

The development and implementation of renewable feedstocks for the production of multifunctional chemicals has received attention from the food and pharmaceutical industries and also as potential raw materials for the manufacture of biodegradable polymers. A major shift towards renewable resources, however, requires new ways to optimize and evaluate industrial processes. There are several possibilities to replace chemical techniques with biological methods based on renewable resources. This review discusses some examples of process development in which a biotechnological route might be favorable leading to industrial realization. Herein are described the production of biomaterials that can be used as monomers in plastics, such as lactic acid for polylactide (PLA), (R)-3-hydroxybutyric acid (R-3HB) for poly[(R)-3-hydroxybutyrate] (PHB), and succinic acid for poly(butylene succinate) (PBS). Moreover, several species of microorganisms that produce significant quantities of these functional chemicals under specific cultivation conditions from biomass-derived carbohydrates are also reviewed.Key words: functional chemicals, renewable resources, lactic acid, (R)-3-hydroxybutyric acid, succinic acid.

L-lactic acid production from apple pomace by sequential hydrolysis and fermentation

The potential of apple pomace (a solid waste from cider and apple juice making factories) as a source of sugars and other compounds for fermentation was evaluated. The effect of the cellulase-to-solid ratio (CSR) and the liquor-to-solid ratio (LSR) on the kinetics of glucose and total monosaccharide generation was studied. Mathematical models suitable for reproducing and predicting the hydrolyzate composition were developed. When samples of apple pomace were subjected to enzymatic hydrolysis, the glucose and fructose present in the raw material as free monosaccharides were extracted at the beginning of the process. Using low cellulase and cellobiase charges (8.5 FPU/g-solid and 8.5 IU/g-solid, respectively), 79% of total glucan was saccharified after 12 h, leading to solutions containing up to 43.8 g monosaccharides/L (glucose, 22.8 g/L; fructose, 14.8 g/L; xylose+mannose+galactose, 2.5 g/L; arabinose+rhamnose, 2.8g/L). These results correspond to a monosaccharide/cellulase ratio of 0.06 g/FPU and to a volumetric productivity of 3.65 g of monosaccharides/L h. Liquors obtained under these conditions were used for fermentative lactic acid production with Lactobacillus rhamnosus CECT-288, leading to media containing up to 32.5 g/L of L-lactic acid after 6 h (volumetric productivity=5.41 g/L h, product yield=0.88 g/g).

Purification and characterization of cellulase produced by Bacillus amyoliquefaciens DL-3 utilizing rice hull

A microorganism hydrolyzing rice hull was isolated from soil and identified as Bacillus amyloliquefaciens by analysis of 16S rDNA and partial sequences of the gyrA gene, and named as B. amyloliquefaciens DL-3. With the analysis of SDS-PAGE, the molecular weight of the purified cellulase was estimated to be 54kDa. The purified cellulase hydrolyzed avicel, caboxymethylcellulose (CMC), cellobiose, beta-glucan and xylan, but not p-Nitrophenyl-beta-D-glucopyranoside (PNPG). Optimum temperature and pH for the CMCase activity of the purified cellulase were found to be 50 degrees C and pH 7.0, respectively. The CMCase activity was inhibited by some metal ions, N-bromosuccinimide and EDTA in the order of Hg(2+)>EDTA>Mn(2+)>N-bromosuccinimide>Ni(2+)>Pb(2+)>Sr(2+)>Co(2+)>K(+). The open reading frame of the cellulase from B. amyloliquefaciens DL-3 was found to encode a protein of 499 amino acids. The deduced amino acid sequence of the cellulase from B. amyloliquefaciens DL-3 showed high identity to cellulases from other Bacillus species, a modular structure containing a catalytic domain of the glycoside hydrolase family 5 (GH5), and a cellulose-binding module type 3 (CBM3).

Brewer’s spent grain as raw material for lactic acid production by Lactobacillus delbrueckii

Chemically pre-treated brewer's spent grain was saccharified with cellulase producing a hydrolysate with approx. 50 g glucose l(-1). This hydrolysate was used as a fermentation medium without any nutrient supplementation by Lactobacillus delbrueckii, which produced L-lactic acid (5.4 g l(-1)) at 0.73 g g(-1) glucose consumed (73% efficiency). An inoculum of 1 g dry cells l(-1) gave the best yield of the process, but the pH decrease affected the microorganism capacity to consume glucose and convert it into lactic acid.

Production of d-lactic acid from sugarcane molasses, sugarcane juice and sugar beet juice by Lactobacillus delbrueckii

Lactobacillus delbrueckii was grown on sugarcane molasses, sugarcane juice and sugar beet juice in batch fermentation at pH 6 and at 40 degrees C. After 72 h, the lactic acid from 13% (w/v) sugarcane molasses (119 g total sugar l(-1)) and sugarcane juice (133 g total sugar l(-1)) was 107 g l(-1) and 120 g l(-1), respectively. With 10% (w/v) sugar beet juice (105 g total sugar l(-1)), 84 g lactic acid l(-1) was produced. The optical purities of D: -lactic acid from the feedstocks ranged from 97.2 to 98.3%.