Characterization of a newly isolated Rubrivivax benzoatilyticus PS-5 with self-flocculation property and optimization pathway for 5-aminolevulinic acid production

Six strains of phototrophic purple non-sulfur bacteria were isolated from paddy soil, lake water and pond sediment samples. They showed the ability to produce 5-aminolevulinic acid under anaerobic-light (3,000 lux) condition. A selected strain, designated as PS-5, produced the highest 5-aminolevulinic acid (ALA) concentration (45.10 μM) and productivity (0.94 μ M h-1) in glutamate-malate (GM) medium as well as possessed self-flocculating ability. Based on physiological and 16S rRNA sequence, the isolate PS-5 was identified to be Rubrivivax benzoatilyticus. The optimum concentration of C4 pathway precursors was 7.5 mM glycine and 10 mM succinate with supplementation of 10 mM levulinic acid. This resulted in 4.2 fold increase of 5-aminolevulinic acid production to 190.74 μM and 2.7-fold increase of its productivity to 2.57 μM h-1 compared to the control. In addition, the optimum concentration of C5 pathway precursor was 50 mM glutamate with the maximum 5-aminolevulinic acid production of 84.12 μM and productivity of 1.56 μM h-1. Therefore, R. benzoatilyticus PS-5 could produce 5-aminolevulinic acid using both C4 and C5 pathway precursors and preferred C4 pathway over C5 pathway as it produced more than 2.3 folds higher 5-aminolevulinic acid concentration.Keywords: 5-Aminolevulinic acid, photosynthetic bacteria, self-flocculation, optimization, Rubrivivax benzoatilyticusAfrican Journal of Biotechnology Vol. 12(16), pp. 2069-208

Nutrient optimization for production of polyhydroxybutyrate from halotolerant photosynthetic bacteria cultivated under aerobic-dark condition

Three halotolerant bacterial strains; Rhodobacter sphaeroides ES16 (the wild type) and the two mutant strains of R. sphaeroides ES16, namely N20 and U7, were cultivated in glutamate-malate (GM) medium and screened for production of polyhydroxybutyrate (PHB). The mutant strains N20 and U7 were found to accumulate PHB (53.9 and 42.0% of DCW, respectively) 3.6 and 2.8 times higher than the wild type strain (19.5% of DCW), respectively. R. sphaeroides N20 were selected for studies on the effects of nutrient and environmental conditions on PHB accumulation. The optimal condition was 4 g/l acetate, 0.02 g/l (NH4)2SO4, C/N ratio of 6:1, 1.0 g/l K2HPO4, 1.0 g/l KH2PO4 and 3% NaCl with initial pH at 7.0. Under this optimal condition, the maximum PHB accumulation increased from 53.9% to 88% of DCW and 9.11 \ub1 0.08 g/l biomass, 8.02 \ub1 0.10 g/l PHB concentration were achieved after 60 hrs cultivation at 37\ubaC. These results are the highest values ever obtained from photosynthetic bacteria reported so far

Micro-aerobic, anaerobic and two-stage condition for ethanol production by Enterobacter aerogenes from biodiesel-derived crude glycerol

The microbial production of ethanol from biodiesel-derived crude glycerol by Enterobacter aerogenes TISTR1468, under micro-aerobic and anaerobic conditions, was investigated. The experimental results showed that micro-aerobic conditions were more favorable for cellular growth (4.0 g/L DCW), ethanol production (20.7 g/L) as well as the ethanol yield (0.47 g/g glycerol) than anaerobic conditions (1.2 g/L DCW, 6.3 g/L ethanol and 0.72 g/g glycerol, respectively). Crude glycerol (100 g/L) was consumed completely with the rate of 1.80 g/L/h. Two-stage fermentation (combination of micro-aerobic and anaerobic condition) exhibited higher ethanol production (24.5 g/L) than using one-stage fermentation (either micro-aerobic or anaerobic condition. The two-stage configuration, exhibited slightly higher crude glycerol consumption rate (1.81 g/L/h), as well as ethanol yield (0.56 g/g) than the one-stage configuration. Therefore, two-stage process was selected for ethanol production from E. aerogenes TISTR1468 in scale-up studies

Biohythane Production from Organic Wastes by Two-Stage Anaerobic Fermentation Technology

The combination of biohydrogen and biomethane production from organic wastes via two-stage anaerobic fermentation could yield a biohythane gas with a composition of 10-15% H2, 50-55% CH4 and 30-40% CO2. Biohythane could be upgraded to biobased hythane by removing of CO2. The two-stage anaerobic fermentation process is based on the different function between acidogens and methanogens in physiology, nutrition needs, growth kinetics, and sensitivity to environmental conditions. In the first stage, the substrate is fermented to H2, CO2, volatile fatty acids (VFA), lactic acid and alcohols by acidogens with optimal pH of 5–6 and hydraulic retention time (HRT) of 1–3 days. In the second stage, the remaining VFA, lactic acid, and alcohols in the H2 effluent are converted to CH4 and CO2 by methanogens under optimal pH range of 7–8 and HRT of 10–15 days. The advantage of biohythane over traditional biogas are more environmentally, flexible of H2/CH4 ratio, higher energy recovery, higher degradation efficiency, shorter fermentation time, and high potential to use as vehicle fuel. This chapter outlines the general approach of biohythane production via two-stage anaerobic fermentation, principles, microorganisms, reactor configuration, process parameters, methods for improving productivity as well as technical challenges toward the scale-up process of biohythane process

Application of statistical experimental methods to optimize medium for exopolymer production by newly isolated Halobacterium sp. SM5

The study investigated on medium optimization for production of exopolymer by a newly isolated bacterium, Halobacterium sp. SM5, using the mixture design and response surface method. The mixture experiment was designed by setting five parameters at the lowest and highest of concentrations: pseudo components design containing 0.15-0.25 glucose, 0.15-0.25 yeast extract, 0.35-0.45 MgSO4\ub77H2O, 0.1-0.2 vitamin casamino acid and 0.02-0.06 KCl. The results of the mixture design revealed that the effect of nutrients or elements on the exopolymer produced by the strain SM5 were in the order of MgSO4\ub77H2O > yeast extract > vitamin casamino acid > KCl > glucose, respectively. The suitable medium recipe for enhancement the exopolymer production was 7.43 g/l glucose, 12.38 g/l yeast extract, 17.33 g/l MgSO4\ub77H2O, 9.9 g/l vitamin casamino acid and 2.48 g/l KCl. The exopolymer to be produced by the strain SM5 was 2.25 g/l, which was higher than that obtained in the original medium (1.3 times). The yield of exopolymer was 2.13 g/l to be obtained in medium containing 7.43 g/l glucose, 11.37 g/l yeast extract, 22.28 g/l MgSO4\ub77H2O, 7.44 g/l vitamin casamino acid and 0.99 g/l KCl which was predicted by response surface methodology. However, under an experiment, the yield of exopolymer was 2.08 \ub1 0.0020 g/l

Enhance 1,3-propanediol production from crude glycerol in batch and fed-batch fermentation with two-phase pH-controlled strategy

The batch fermentation of 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae SU6 at different crude glycerol concentration (40-100 g l-1), pH (6.5-7.5) and temperature (31-40\ubaC) combined with two-phase pH-controlled strategy was investigated. Effect of feeding rate (0.10-0.15 L h-1) was studied in fed-batch fermentation. In batch fermentation, the optimal condition was 60 g l-1 crude glycerol, pH control at 6.5 and cultivation temperature at 37\ubaC. The maximum 1,3-PD of 20 g l-1, the yield of 0.34 g 1,3-PD g-1 glycerol consumed and the productivity of 1.25 g l-1 h-1 were achieved at 16 hrs cultivation. The by-products were acetic acid and succinic acid at 2.7 and 1.1 g l-1, respectively. Two-phase pH-controlled strategy gave better results (24.95 g l-1 1,3-PD and 1.78 g l-1 h-1 productivity) than constant pH-controlled strategy (20 g l-1 and 1.25 g l-1 h-1, respectively) at 16 hrs incubation. In fed-batch fermentation, the maximum 1,3-PD of 45.35 g l-1 was achieved at constant feeding rate of 0.1 L h-1. The yield and productivity were 0.44 g g-1 and 1.94 g l-1 h-1, respectively. The fed-batch fermentation with constant feeding at 0.1 L h-1 with two-phase pH-controlled strategy gave 2.2 folds higher 1,3 PD concentration than the batch fermentation with two-phase pH-controlled strategy. This demonstrated the great impact of combination of pH control and feeding strategies in fed-batch fermentation on enhancing 1,3-propanediol production

Application of palm pressed fiber as a carrier for ethanol production by Candida shehatae TISTR5843

Abstract Palm pressed fiber (PPF) is a clean and renewable lignocellulosic material. The PPF and delignified PPF (DPPF) were used as a carrier for immobilization of Candida shehatae TISTR5843 in bioethanol production. PPF was pre-treated by milling to obtain small particles, whereas DPPF was the delignification of PPF using NaClO2. C. shehatae TISTR5843 was grown in modified yeast extract- malt (YM) medium at 30 \ub1 2\ubaC on an orbital shaker at 150 rpm for batch and repeated batch fermentation. In the batch system, immobilized cells on a small size, less than 0.5 mm, of DPPF (sDPPF) gave the maximum ethanol production of 11.5 g L-1 at 24 hrs cultivation period. The ethanol concentration and ethanol yield of sDPPF were 6.2% and 6.8% higher (ethanol production 11.5 g L-1, ethanol yield 0.47 g g-1) than those of free cells (ethanol production 10.8 g L-1, ethanol yield 0.44 g g-1) after 36 hrs of cultivation. In contrast, the small size of PPF (sPPF) was selected as a carrier in repeated batch fermentation for cost effectiveness. The ethanol productivity of immobilized yeast cells in repeated batch fermentations was 45.2-51.6% greater than that obtained from batch fermentations. The immobilized cells on sPPF improved the ethanol production and could be reused 4 times with retaining the activity of 93%. In conclusion, PPF is a potential carrier in the immobilization system. The pre-treatment of PPF increases the surface area that enhances cell adsorption and ethanol production by C. shehatae TISTR5843

Dilute Acid Pretreatment of Oil Palm Trunk Biomass at High Temperature for Enzymatic Hydrolysis

AbstractOld oil palm trunk (OPT) is available in large quantity in Southeast Asia and a potential lignocellulosic biomass resource for bioethanol production. Dilute acid (DA) pretreatment was applied to the old oil palm trunk for enzymatic saccharification. The pretreatment conditions were investigated through a fractional factorial experiment design. The pretreated substrates were analyzed for chemical composition, and their enzymatic digestibility was investigated and compared. The results indicated that the DA pretreatment was able to improve enzymatic hydrolysis by removing hemicelluloses from OPT. Mild pretreatment preserved more hemicellulose and cellulose in pretreated OPT, but severe pretreatment was necessary to achieve satisfactory enzymatic hydrolysis of OPT. For example, the DA pretreatment with 3% H2SO4 at 180°C for 40min could achieve an 80% enzymatic hydrolysis