Effect of glutaraldehyde biocide on laboratory-scale rotating biological contactors and biocide efficacy

The effect of glutaraldehyde, a commercial biocide widely used in paper and pulp industry, on the performance of laboratory-scale rotating biological contactors (RBCs) as well as biocide efficacy was studied. Biofilms were established on the RBCs and then exposed to 0 - 180 ppm glutaraldehyde at a dilution rate of 1.60 h-1. The results showed that the biofilms became acclimated to glutaraldehyde and eventually could degrade it. Acclimation to the biocide took longer at the higher biocide concentrations. The degree of biocide degradation and chemical oxygen demand (COD) removal depended on acclimation period, the presence of other organic matters and the amount of mineral salts available. Glutaraldehyde at up to 80 ppm had no effect on treatment efficiency and populations of biofilms and planktonic phase of the system whereas glutaraldehyde at 180 ppm caused a progressive decline in all measured values. However, no glutaraldehyde concentration used in the study was sufficiently high to kill microorganisms in the RBC system. The presence of biofilm provided additional resistance to glutaraldehyde to bacteria because the biocide had to penetrate through biofilm to reach bacteria. The increased resistance of bacteria to glutaraldehyde due to acclimation should be considered in biocide applications

The use of dried spent yeast as a low-cost nitrogen supplement in ethanol fermentation from sweet sorghum juice under very high gravity conditions

Dried spent yeast (DSY) was used as a low-cost nitrogen supplement for ethanol fermentation from sweet sorghum juice under very high gravity (VHG) conditions by Saccharomyces cerevisiae NP 01. The fermentation was carried out at 30\ubaC in a 5-litre bioreactor. The results showed that DSY promoted ethanol production efficiencies. The ethanol concentration (P), productivity (Qp) and yield (Yp/s) of the sterile juice (total sugar of 280 g l-1) supplemented with 8 g l-1 of DSY were not different from those supplemented with yeast extract and/or peptone at the same amount. The initial yeast cell concentration of 5 x 107 cells ml-1 was found to be optimal for scale-up ethanol production. In addition, an increase in sugar concentration in inoculum preparation medium (from 10 to 100 g l-1) improved the ability of the inoculum to produce ethanol under the VHG conditions. When S. cerevisiae NP 01 grown in the juice containing 100 g l-1 of total sugar was used as the inoculum for ethanol fermentation, the P, Qp and Yp/s obtained were 108.98 \ub1 1.16 g l-1, 2.27 \ub1 0.06 g l-1 h-1 and 0.47 \ub1 0.01 g g-1, respectively. Similar results were also observed when the ethanol fermentation was scaled up to a 50-litre bioreactor under the same conditions. The cost of the sweet sorghum for ethanol production was US$ 0.63 per litre of ethanol. These results clearly indicate the high potential of using sweet sorghum juice supplemented with DSY under VHG fermentation for ethanol production in industrial applications

Ethanol production from sweet sorghum juice under very high gravity conditions: Batch, repeated-batch and scale up fermentation

Batch ethanol fermentations from sweet sorghum juice by Saccharomyces cerevisiae NP 01 were carried out in a 500 ml air-locked Erlenmeyer flask under very high gravity (VHG) and static conditions. The maximum ethanol production efficiency was obtained when 9 g l-1 of yeast extract was supplemented to the juice. The ethanol concentration (P), productivity (Qp) and yield (Yp/s) were 120.24 \ub1 1.35 g l-1, 3.01 \ub1 0.08 g l-1 h-1 and 0.49 \ub1 0.01, respectively. Scale up ethanol fermentation in a 5-litre bioreactor at an agitation rate of 100 rev min-1 revealed that P, Qp and Yp/s were 139.51 \ub1 0.11 g l-1, 3.49 \ub1 0.00 g l-1 h-1 and 0.49 \ub1 0.01, respectively, whereas lower P (119.53 \ub1 0.20 g l-1) and Qp (2.13 \ub1 0.01 g l-1 h-1) were obtained in a 50-litre bioreactor. In the repeated-batch fermentation in the 5-litre bioreactor with fill and drain volume of 50% of the working volume, lower P and Qp were observed in the subsequent batches. P in batch 2 to 8 ranged from 103.37 \ub1 0.28 to 109.53 \ub1 1.06 g l-1

Repeated-Batch Ethanol Fermentation from Sweet Sorghum Stem Juice under a Very High Gravity Condition Using a Stirred Tank Bioreactor Coupled with a Column Bioreactor by Immobilized <i>Saccharomyces cerevisiae</i>

The ethanol fermentation efficiency of sweet sorghum stem juice (SSJ) under a very high gravity (VHG) condition (250 g/L of sugar) was improved by immobilized Saccharomyces cerevisiae SSJKKU01, using a stirred tank bioreactor (STR) coupled with a column bioreactor (CR). Dried rattan pieces (as carriers for cell immobilization) at 50% of the working volume of the CR were suitable for use in a batch ethanol fermentation. The average ethanol concentration (PE) and ethanol productivity (QP) of repeated-batch fermentation in the CR for eight successive cycles were 109.85 g/L and 1.88 g/L⋅h, respectively. Then an STR coupled with a CR was applied for repeated-batch ethanol fermentation in two systems. System I was an STR (1.8 L working volume), and System II was an STR (1 L) coupled with a CR, referred to as a CR-F (0.8 L). Both systems were connected to a new CR, called CR-I, containing sterile dried rattan pieces at 50% of its working volume. Active yeast cells were inoculated only into the STR, and the medium circulation rate between bioreactors was 5.2 mL/min. The results showed that at least eight successive cycles could be operated with an average PE of 108.51 g/L for System I and 109.44 g/L for System II. The average QP and SC values of both systems were also similar, with values of 1.87 to 1.88 g/L⋅h and 93 to 94%, respectively. The morphology of the carriers with and without immobilized cells before and after the fermentation was investigated. The obtained results demonstrated that a repeated-batch fermentation by immobilized cells on rattan pieces, using an STR coupled with a CR, was successfully used to produce high levels of ethanol from SSJ under a VHG condition

An Alternative Approach to Improve the Butanol Production Efficiency from Sweet Sorghum Stem Juice Using Immobilized Cells Combined with an In Situ Gas Stripping System

The effects of the nitrogen source and buffers used in butanol production with Clostridium beijerinckii TISTR 1461 from sweet sorghum stem juice (SSJ) containing 60 g/L of total sugar were first studied in this paper. Among the various nitrogen sources (dried spent yeast, urea, ammonium acetate, ammonium sulfate), urea was found to be the most suitable for butanol production. SSJ supplemented with urea (0.64 g/L) and cocktail buffers (KH2PO4, 0.5 g/L; K2HPO4, 0.5 g/L; ammonium acetate, 2.2 g/L) gave the highest butanol concentration (PB, 10.13 g/L). Then, the capability of immobilized C. beijerinckii TISTR 1461 cells for butanol fermentation was investigated. Two residual waste materials were examined as immobilized cell carriers. Bamboo chopstick pieces were more appropriate as carriers for cell immobilization than cigarette filter tips. The PB value of the immobilized cells on the bamboo chopstick pieces was ~13% higher than that on the cigarette filter tips. Using the response surface methodology (RSM), 1.9 cm bamboo chopstick pieces with a carrier loading of 1:32 (w/v) were the optimum conditions for cell immobilization for butanol production. Under these conditions, the PB value was 11.62 g/L. To improve the butanol production efficiency, a gas stripping system (GS) was connected to the fermenter. It was found that the PB (14.02 g/L) and butanol productivity (QB, 0.29 g/L&middot;h) values improved by ~21% compared to butanol fermentation using no gas stripping

An Alternative Approach to Improve the Butanol Production Efficiency from Sweet Sorghum Stem Juice Using Immobilized Cells Combined with an In Situ Gas Stripping System

The effects of the nitrogen source and buffers used in butanol production with Clostridium beijerinckii TISTR 1461 from sweet sorghum stem juice (SSJ) containing 60 g/L of total sugar were first studied in this paper. Among the various nitrogen sources (dried spent yeast, urea, ammonium acetate, ammonium sulfate), urea was found to be the most suitable for butanol production. SSJ supplemented with urea (0.64 g/L) and cocktail buffers (KH2PO4, 0.5 g/L; K2HPO4, 0.5 g/L; ammonium acetate, 2.2 g/L) gave the highest butanol concentration (PB, 10.13 g/L). Then, the capability of immobilized C. beijerinckii TISTR 1461 cells for butanol fermentation was investigated. Two residual waste materials were examined as immobilized cell carriers. Bamboo chopstick pieces were more appropriate as carriers for cell immobilization than cigarette filter tips. The PB value of the immobilized cells on the bamboo chopstick pieces was ~13% higher than that on the cigarette filter tips. Using the response surface methodology (RSM), 1.9 cm bamboo chopstick pieces with a carrier loading of 1:32 (w/v) were the optimum conditions for cell immobilization for butanol production. Under these conditions, the PB value was 11.62 g/L. To improve the butanol production efficiency, a gas stripping system (GS) was connected to the fermenter. It was found that the PB (14.02 g/L) and butanol productivity (QB, 0.29 g/L·h) values improved by ~21% compared to butanol fermentation using no gas stripping

Butanol Production by a Novel Efficient Method Using Mixed Cultures of <i>Clostridium beijerinckii</i> and <i>Arthrobacter</i> sp. in Stirred-Tank and Gas-Lift Bioreactors

Arthrobacter sp. BCC 72131, an obligate aerobic bacterium, was used to create anaerobic conditions, and Clostridium beijerinckii TISTR 1461 was used as a butanol producer in an acetone-butanol–ethanol (ABE) fermentation. Sweet sorghum juice (SSJ) medium containing 60 g/L of total sugar supplemented with 1.27 g/L of (NH4)2SO4 was used as a butanol production (BP) medium. Arthrobacter sp. was inoculated into the BP medium in 1-L screw-capped bottles. After 2, 4, 6 and 12 h of Arthrobacter sp. cultivation at 30 °C, C. beijerinckii was transferred into the BP medium to start butanol production at 37 °C. The results showed that C. beijerinckii inoculation after 6 h of Arthrobacter sp. cultivation gave the highest butanol titer (PB) at 12.56 g/L, with a butanol yield (YB/S) and volumetric butanol productivity (QB) of 0.34 g/g and 0.23 g/L·h, respectively. These values are approximately 10–27% higher than those of the control experiment using a single culture of C. beijerinckii TISTR 1461 and oxygen-free nitrogen (OFN) gas flushing to create anaerobic conditions. Field emission scanning electron microscopic (FE-SEM) images of Clostridium cells, as well as protein and free amino nitrogen concentrations in the broth during butanol fermentation were also studied to confirm the results. The butanol fermentation was then carried out in a 5.6-L stirred-tank and a 1.2-L low-cost gas-lift bioreactor by the mixed cultures using the optimal time of Clostridium inoculation. The PB, YB/S and QB values obtained were not significantly different from those in the 1-L screw-capped bottles. Hence, Arthrobacter sp. can be used as a novel method to create anaerobic conditions instead of a traditional method employing OFN gas flushing. Using mixed cultures of Arthrobacter sp. BCC 72131 and C. beijerinckii TISTR 1461 is a practical method to produce butanol on a large-scale, both in complex and low-cost bioreactors

Repeated-Batch Ethanol Fermentation from Sweet Sorghum Stem Juice under a Very High Gravity Condition Using a Stirred Tank Bioreactor Coupled with a Column Bioreactor by Immobilized Saccharomyces cerevisiae

The ethanol fermentation efficiency of sweet sorghum stem juice (SSJ) under a very high gravity (VHG) condition (250 g/L of sugar) was improved by immobilized Saccharomyces&nbsp;cerevisiae SSJKKU01, using a stirred tank bioreactor (STR) coupled with a column bioreactor (CR). Dried rattan pieces (as carriers for cell immobilization) at 50% of the working volume of the CR were suitable for use in a batch ethanol fermentation. The average ethanol concentration (PE) and ethanol productivity (QP) of repeated-batch fermentation in the CR for eight successive cycles were 109.85 g/L and 1.88 g/L&sdot;h, respectively. Then an STR coupled with a CR was applied for repeated-batch ethanol fermentation in two systems. System I was an STR (1.8 L working volume), and System II was an STR (1 L) coupled with a CR, referred to as a CR-F (0.8 L). Both systems were connected to a new CR, called CR-I, containing sterile dried rattan pieces at 50% of its working volume. Active yeast cells were inoculated only into the STR, and the medium circulation rate between bioreactors was 5.2 mL/min. The results showed that at least eight successive cycles could be operated with an average PE of 108.51 g/L for System I and 109.44 g/L for System II. The average QP and SC values of both systems were also similar, with values of 1.87 to 1.88 g/L&sdot;h and 93 to 94%, respectively. The morphology of the carriers with and without immobilized cells before and after the fermentation was investigated. The obtained results demonstrated that a repeated-batch fermentation by immobilized cells on rattan pieces, using an STR coupled with a CR, was successfully used to produce high levels of ethanol from SSJ under a VHG condition