Rice Bran Hydrolysate Research Articles

Development of rice bran treatment process and its use for the synthesis of polyhydroxyalkanoates from rice bran hydrolysate solution

Rice bran treatment process for the production of 43.7kg of hydrolysate solution containing 24.41g/L of glucose and small amount of fructose from 5kg of rice bran was developed and employed to produce polyhydroxyalkanoates in recombinant Escherichia coli and Ralstonia eutropha strains. Recombinant E. coli XL1-Blue expressing R. eutropha phaCAB genes and R. eutropha NCIMB11599 could produce poly(3-hydroxybutyrate) with the polymer contents of 90.1wt% and 97.2wt%, respectively, when they were cultured in chemically defined MR medium and chemically defined nitrogen free MR medium containing 10mL/L of rice bran hydrolysate solution, respectively. Also, recombinant E. coli XL1-Blue and recombinant R. eutropha 437-540, both of which express the Pseudomonas sp. phaC1437 gene and the Clostridium propionicum pct540 gene could produce poly(3-hydroxybutyrate-co-lactate) from rice bran hydrolysate solution. These results suggest that rice bran may be a good renewable resource for the production of biomass-based polymers by recombinant microorganisms.

Continuous l-lactic acid production from defatted rice bran hydrolysate using corn stover bagasse immobilized carrier

In this paper, l-lactic acid (LLA) was produced using defatted rice bran hydrolysate.

English

The suitability of crude glycerol (75% (v/v) glycerol content) from a biodiesel production plant, and soybean meal and rice bran hydrolysates as replacements in the culture medium for commercially available glycerol, peptone and yeast extract, respectively, to form a low cost culture medium for the growth of, and recombinant endoglucanase II production by, Pichia pastoris was evaluated. The use of 1% (v/v) crude glycerol as a carbon source, and a mixture of 0.175% (v/v) soybean meal and 0.15% (v/v) rice bran hydrolysate in the presence of 0.5% (w/v) ammonium sulfate was found to be a suitable medium in the presence of 3% (v/v) methanol as the inducer. Under these conditions, the highest level of extracellular endoglucanase II activity (61.5 U/mL) was found after 120 h culture at 30°C and pH 6.0.  Key words: Biodiesel glycerol, soybean meal, rice bran, endoglucanase II, Pichia pastoris.

Biofilm production by Zymomonas mobilis enhances ethanol production and tolerance to toxic inhibitors from rice bran hydrolysate

Microorganisms play a significant role in bioethanol production from lignocellulosic material. A challenging problem in bioconversion of rice bran is the presence of toxic inhibitors in lignocellulosic acid hydrolysate. Various strains of Zymomonas mobilis (ZM4, TISTR 405, 548, 550 and 551) grown under biofilm or planktonic modes were used in this study to examine their potential for bioconversion of rice bran hydrolysate and ethanol production efficiencies. Z. mobilis readily formed bacterial attachment on plastic surfaces, but not on glass surfaces. Additionally, the biofilms formed on plastic surfaces steadily increased over time, while those formed on glass were speculated to cycle through accumulation and detachment phases. Microscopic analysis revealed that Z. mobilis ZM4 rapidly developed homogeneous biofilm structures within 24 hours, while other Z. mobilis strains developed heterogeneous biofilm structures. ZM4 biofilms were thicker and seemed to be more stable than other Z. mobilis strains. The percentage of live cells in biofilms was greater than that for planktonic cells (54.32 ± 7.10% vs. 28.69 ± 3.03%), suggesting that biofilms serve as a protective niche for growth of bacteria in the presence of toxic inhibitors in the rice bran hydrolysate. The metabolic activity of ZM4 grown as a biofilm was also higher than the same strain grown planktonically, as measured by ethanol production from rice bran hydrolysate (13.40 ± 2.43 g/L vs. 0.432 ± 0.29 g/L, with percent theoretical ethanol yields of 72.47 ± 6.13% and 3.71 ± 5.24% respectively). Strain TISTR 551 was also quite metabolically active, with ethanol production by biofilm and planktonically grown cells of 8.956 ± 4.06 g/L and 0.0846 ± 0.064 g/L (percent theoretical yields were 48.37 ± 16.64% and 2.046 ± 1.58%, respectively). This study illustrates the potential for enhancing ethanol production by utilizing bacterial biofilms in the bioconversion of a readily available and normally unusable low value by-product of rice farming.

Biohydrogen production from ricebran using Clostridium saccharoperbutylacetonicum N1-4

Treated ricebran hydrolysate was fermented anaerobically using Clostridium saccharoperbutylacetonicum N1-4 at an initial pH of 6 ± 0.2 and an operating temperature of 30 °C for production of hydrogen. The effects of different pretreatment methods on the liberation of sugar from 100 g of ricebran per litre of medium (distilled water) were investigated. In addition, the effects of the pretreatment method on ricebran hydrolysates of different initial ricebran concentrations on liberated sugar as well as the effects of the initial inoculum concentration, ricebran (substrate) concentration, and FeSO4·7H2O concentration on the yield as well as the productivity of hydrogen were investigated. The combination of enzymatic hydrolysis and a boiling pretreatment method produced the most fermentable sugar, 29.03 ± 0.0 g/L from 100 g of ricebran per litre of medium (distilled water), while the amount of sugar liberated by ricebran hydrolysates of different initial ricebran concentrations upon pretreatment monotonically increased with the initial ricebran concentration. The increment in substrate, inoculum, and FeSO4·7H2O concentrations had a significantly positive effect (p < 0.05) on both the yield and productivity of hydrogen. The maximum hydrogen gas yield (YP/S) and productivity of 3.37 mol-H2 per mol-sugar consumed and 7.58 mmol/(L h), respectively, were obtained from ricebran hydrolysate with a 100 g/L ricebran concentration (equivalent to 28.59 ± 1.27 g sugar/L). In other experiments, 0.03 g/L FeSO4·7H2O and 1.5 g/L inoculum resulted in the best hydrogen gas yield and productivity from ricebran hydrolysates.

The Composition of Rice Bran Hydrolysate and Its Possibility to Use in the Ethanol Production by Zymomonas mobilis Biofilm

The Composition of Rice Bran Hydrolysate and Its Possibility to Use in the Ethanol Production by Zymomonas mobilis Biofilm

Oil Production fromYarrowia lipolyticaPo1g Using Rice Bran Hydrolysate

The purpose of this study was to produce microbial oil from Yarrowia lipolytica Po1g grown in defatted rice bran hydrolysate. After removing oil from rice bran by Soxhlet extraction, the bran is subjected to acid hydrolysis with various sulfuric acid concentrations (1–4% v/v), reaction times (1–8 h), and reaction temperatures (60–120°C). The optimal conditions for maximum total sugar production from the hydrolysate were found to be 3% sulfuric acid at 90°C for 6 h. Glucose was the predominant sugar (43.20 ± 0.28 g/L) followed by xylose (4.93 ± 0.03 g/L) and arabinose (2.09 ± 0.01 g/L). The hydrolysate was subsequently detoxified by neutralization to reduce the amount of inhibitors such as 5-hydroxymethylfurfural (HMF) and furfural to increase its potential as a medium for culturing Y. lipolytica Po1g. Dry cell mass and lipid content of Y. lipolytica Po1g grown in detoxified defatted rice bran hydrolysate (DRBH) under optimum conditions were 10.75 g/L and 48.02%, respectively.

Exploration of rice bran, an agro-industry residue, for the production of intra- and extra-cellular polymers by Sinorhizobium meliloti MTCC 100

The present work was focused on simultaneous production of certain intra- and extra-cellular polymers by fast growing Sinorhizobium meliloti MTCC 100 using ricebran, a low cost agro-industry residue, in hydrolyzed form to enhance product yields. The culture produced 3.63 g/L of biomass, 1.75 g/L of intra-cellular polymer (polyhydroxyalkanoate, PHA) and 1.2 g/L of extra-cellular polymer (exopolysaccharide, EPS) in control, polymer production (PP) medium. Supplementation of 20% ricebran hydrolysate (RBH) to PP medium at 0 h resulted in increased production of biomass, PHA and EPS (5.92, 2.71 and 2.01 g/L, respectively). Addition of RBH at after 24 h of fermentation increased the amount of EPS by 5 folds after 72 h at 30 °C. An initial pH of 7.0 and fermentation temperature of 30 °C were found to be optimum for the production of biomass as well as both the biopolymers. The biomass, PHA and EPS contents increased with the increase in fermentation period from 24 h to 72 h, with a maximum biomass of 7.45 g/L and PHA of 3.60 g/L. With further incubation to 96 h EPS production increased to 11.8 g/L. Gas chromatography and Fourier transform infra red spectroscopy of the PHA indicated it to be a copolymer of polyhydroxybutyrate and polyhydroxyvalerate.

Effect of Different Pretreatment Methods on the Bioconversion of Rice Bran into Ethanol

The efficiency of acid, enzyme and microbial pretreatment of rice bran was compared based on the content of cellulose, hemicellulose, reducing sugars and xylose in the substrate. An isolate of Aspergillus niger or a strain of Trichoderma viride (MTCC 800) was employed for microbial pretreatment of rice bran in solid state. Acid pretreatment resulted in the highest amount of reducing sugars followed by enzyme and microbial pretreatment. A. niger showed a higher rate of hydrolysis than T. viride. The rice bran hydrolysate obtained from the different methods was subsequently fermented to ethanol either by Zymomonas mobilis (NCIM 806) or by Pichia stipitis (NCIM 3497). P stipitis fermentation resulted in higher ethanol (37% higher) and biomass production (76~83% higher) than those of Z. mobilis. Maximum ethanol production resulted at 12 h in Zymomonas fermentation, while in Pichia fermentation, it was observed at 60 h. Microbial pretreatment of rice bran by A. niger followed by fermentation employing P. stipitis was more efficient but slower than the other microbial pretreatment and fermentation.