Extracellular protease derived from lactic acid bacteria stimulates the fermentative lactic acid production from the by-products of rice as a biomass refinery function.
A lactic acid producing bacterium, Lactobacillus rhamnosus M-23, newly isolated from a rice washing drainage storage tank was found to produce l-(+)-lactic acid from a non-sterilized mixture of rice washing drainage and rice bran without any additions of nutrients under the simultaneous saccharification and fermentation (SSF) process. This strain has the ability to utilize the non-sterilized rice washing drainage and rice bran as a source of carbohydrate, saccharifying enzymes and nutrients for lactic acid production. Observation of extracellular protease activity in SSF culture broth showed that a higher protease activity was present in strain M-23 than in other isolated lactic acid producing bacteria (LABs). To investigate the structural changes of solid particles of rice washing drainage throughout LAB cultivation, scanning electron microscopic (SEM) observation and Fourier transform infrared-spectroscopy (FT-IR) analysis were performed. The results of the SEM observation showed that the surface material could be removed from solid particles of rice washing drainage treated by culture broth (supernatant) of strain M-23, thus exposing the crystal structure of the starch particle surface. The results of the FT-IR analysis revealed that the specific transmittance decrease of the CC and CO stretching and OH group of the solid particles of the rice washing drainage were highly correlated with the produced lactic acid concentration and extracellular protease activity, respectively. These results demonstrate the high lactic acid producing ability of strain M-23 from a non-sterilized mixture of rice washing drainage and rice bran under the SSF condition due to the removal of proteinaceous material and exposure of the starch particle surface by extracellular protease.
Department of Food, Life and Environmental Science, Faculty of Agriculture, Yamagata University, 1-23 Wakaba-machi, Tsuruoka, Yamagata 997-8555, Japan. Electronic address: mwata@tds1.tr.yamagata-u.ac.jp.
Masanori
M
Watanabe
Bioprocess Research Cluster, The School of Agro-Industry, Faculty of Agro-Industry, Chiang Mai University, Mae-Hea, Mueang, Chiang Mai 50100, Thailand.
Charin
C
Techapun
Bioprocess Research Cluster, The School of Agro-Industry, Faculty of Agro-Industry, Chiang Mai University, Mae-Hea, Mueang, Chiang Mai 50100, Thailand.
Ampin
A
Kuntiya
Bioprocess Research Cluster, The School of Agro-Industry, Faculty of Agro-Industry, Chiang Mai University, Mae-Hea, Mueang, Chiang Mai 50100, Thailand.
Noppol
N
Leksawasdi
Bioprocess Research Cluster, The School of Agro-Industry, Faculty of Agro-Industry, Chiang Mai University, Mae-Hea, Mueang, Chiang Mai 50100, Thailand.
Phisit
P
Seesuriyachan
Bioprocess Research Cluster, The School of Agro-Industry, Faculty of Agro-Industry, Chiang Mai University, Mae-Hea, Mueang, Chiang Mai 50100, Thailand.
Thanongsak
T
Chaiyaso
Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan.
Shinji
S
Takenaka
Graduate School of Agricultural Science, Utsunomiya University, 350 Minemachi, Utsunomiya 321-8505, Japan.
Isamu
I
Maeda
Department of Bioscience and Biotechnology, Graduate School of Agriculture, Shinshu University, Minamiminowamura, Nagano 399-4598, Japan.
Masahiro
M
Koyama
Department of Bioscience and Biotechnology, Graduate School of Agriculture, Shinshu University, Minamiminowamura, Nagano 399-4598, Japan.
Kozo
K
Nakamura
D018533:Biomass; D010450:Endopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D005285:Fermentation; D019344:Lactic Acid / Q000096:biosynthesis*; D007778:Lactobacillus / Q000201:enzymology; D052201:Lacticaseibacillus rhamnosus / Q000201:enzymology*; D012275:Oryza / Q000737:chemistry / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared; D013213:Starch / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism
D019344:Lactic Acid; D013395:Sucrose; D013213:Starch; D010450:Endopeptidases
Lactic acid; Protease; Rice bran; Rice washing drainage; Simultaneous saccharification and fermentation