Senthilkumar Sivaprakasam

Biological treatment of tannery wastewater by using salt-tolerant bacterial strains

BackgroundHigh salinity (1–10% w/v) of tannery wastewater makes it difficult to be treated by conventional biological treatment. Salt tolerant microbes can adapt to these saline conditions and degrade the organics in saline wastewater.ResultsFour salt tolerant bacterial strains isolated from marine and tannery saline wastewater samples were identified as Pseudomonas aeruginosa, Bacillus flexus, Exiguobacterium homiense and Staphylococcus aureus. Growth factors of the identified strains were optimized. Tannery saline wastewater obtained from a Common Effluent Treatment Plant (CETP) near Chennai (southern India) was treated with pure and mixed consortia of four salt tolerant bacterial strains. Experiments with optimized conditions and varying salt content (between 2 and 10% (w/v) were conducted. Salt inhibition effects on COD removal rate were noted. Comparative analysis was made by treating the tannery saline wastewater with activated sludge obtained from CETP and with natural habitat microbes present in raw tannery saline wastewater.ConclusionSalt tolerant bacterial mixed consortia showed appreciable biodegradation at all saline concentrations (2%, 4%, 6%, 8% and 10% w/v) with 80% COD reduction in particular at 8% salinity level the consortia could be used as suitable working cultures for tannery saline wastewater treatment.

Biocalorimetric and respirometric studies on metabolic activity of aerobically grown batch culture ofPseudomonas aeruginosa

Biocalorimetry has proved to be a useful tool for scale up and control of bioreactors. The findings reported here are fundamental data required for scale up and control of a reactor for the treatment of saline tannery wastewater. The study deals with biokinetics of a halo-tolerant bacteriaPseudomonas aeruginosa isolated from tannery saline wastewater (soak liquor). Batch experiments were performed in a biocalorimeter and the isolated strain was grown in a glucose-limited mineral salt medium (MSM) at optimized growth conditions. Tessier model is found to fit well for the growth ofP. aeruginosa in biocalorimeter. Biokinetic constants are evaluated and simulation is done to validate experimental results with theoretical values. Respirogram and heat profiles are seen to follow the biomass growth curve. Oxycalorific coefficient is validated with the theoretical values and those noticed in the published literature. There is a good correlation between experimentally determined heat yields and the theoretical values predicted by elemental and enthalpy balances. The heat yield and biomass yield values indicated the behavior of the isolated organism in a substrate-limited well defined growth media (MSM)

The choice of suitable online analytical techniques and data processing for monitoring of bioprocesses.

With increasing pressure from regulatory authorities on industry to develop processes embracing process analytical technology (PAT) initiatives, there is a growing demand to establish reliable tools and systems capable of meeting this need. With regard to monitoring and control of bioprocesses, this need translates to a search for robust instrumentation capable of monitoring the critical process parameters in real time. The application of such technologies at all stages of the process, from the initial R&D phase to process optimisation and production, enhances process understanding and paves the way for the development of control platforms. An examination of the PAT concept and selected tools (NIR, MIR, Raman, dielectric spectroscopy and calorimetry) are presented here. A description of each tool is given, with particular emphasis on the nature of the signal produced and how these relate to measurements of biomass, metabolites and product. A description of the signal processing that is necessary to gain meaningful results from the different tools is also given, together with online data reconciliation techniques based on mass and energy balances. Many techniques such as those based on vibrational spectroscopy are of particular interest, since they are capable of monitoring several critical process parameters which are typically controlled in a bioprocess. A window of application for each of the techniques, when used in the area of bioprocessing, is suggested based on their uses and inherent limitations.

Enhanced production of optically pure d (–) lactic acid from nutritionally rich Borassus flabellifer sugar and whey protein hydrolysate based–fermentation medium

The aim of this study is to optimize the production of optically pure d (–) lactic acid (DLA) employing a cost‐effective production medium. Based on the designed biomass approach, Sporolactobacillus inulinus NBRC 13595 was found to exhibit high DLA titer (19.0 g L−1) and optical purity (99.6%). A cost‐effective medium was constituted using Palmyra palm jaggery (PJ) from Borassus flabellifer and whey protein hydrolysate (WPH) as carbon and nitrogen sources, respectively. Plackett–Burman design indicated that PJ, WPH, and MnSO4 as significant variables influence DLA production. A rotatable central composite design and response surface methodology were used to optimize the PJ and WPH concentrations. A maximum DLA titer (170.14 g L−1) was predicted for 222.24 g L−1 of PJ and 11.99 g L−1 of WPH, respectively. Fermentation experimental results exhibited a maximum DLA titer (189.0 ± 8.53 g L−1) and productivity (5.25 ± 0.24 g L−1 H−1), which is the highest ever reported for DLA production from a renewable feedstock in the batch process. The present investigation substantiates that the potential application of economically viable raw feedstocks (PJ and WPH) for enhanced DLA production, which is attributed to 2.5‐fold reduction in DLA production cost compared with conventional medium.

Oxygen mass transfer studies on batch cultivation of P. aeruginosa in a biocalorimeter

In the present work volumetric mass transfer coefficient (kLa) was investigated during batch cultivations of Pseudomonas aeruginosa on a nutrient media. The effects of process variables (viz. impeller speed, oxygen flow and geometry of impeller) on the volumetric mass transfer coefficient of oxygen, kLa, in a biocalorimeter (Bio-RC1) was investigated and reported in this research work. The experimental data have been analyzed employing MATLAB to obtain the influences of the process parameters on kLa. An attempt was made to correlate volumetric mass transfer coefficient with metabolic heat production rate at optimized process conditions. The correlation reported in this work would be useful to control and scale up of bioprocesses. With the recent activities for developing biological

Biocalorimetric Studies of the Metabolic Activity of Pseudomonas aeruginosa Aerobically Grown in a Glucose-Limited Complex Growth Medium

Biocalorimetric experiments were performed to investigate the aerobic growth of Pseudomonas aeruginosa, isolated from tannery saline wastewater. Growth factors (pH, Inoculum size, carbon source, temperature, aeration rate, and agitation rate) were optimized in shaker and calorimeter based on the growth of P. aeruginosa and heat generation rates. A limiting value of 0.2% glucose concentration was found to be optimum for the growth of P. aeruginosa in a complex growth medium, and the heat flux (qr) profiles resulting from the metabolic activity of P. aeruginosa further confirmed this observation. The bacterial growth profile was found to correlate well with the metabolic heat generated. Heat-yield values were calculated for both glucose consumption and the growth of P. aeruginosa from the calorimetric results. Metabolic shifts in substrate uptake from glucose to peptone present in growth medium was observed by the variations in heat-flux profile. The calorimetric data presented in this study should be useful in understanding the behavior of the isolated bacterial strain in degrading complex and mixed substrates commonly observed in tannery saline waste stream, and further to extend the results for scale-up studies.

Biosorption of lead using Bacillus badius AK strain isolated from compost of green waste (water hyacinth)

ABSTRACT The bacterial strain Bacillus badius AK isolated from water hyacinth compost was investigated for biosorption characteristics in Pb(II) removal. Batch mode experiments depicted the optimum conditions for biosorption as pH at 4, the temperature of 30°C, 150 rpm of the rotational speed at biomass concentration of 20 mL with 1.7 × 1016 colony forming unit per milliliter (CFU/mL) value, at 100–150 mg/L concentration of Pb(II). The bacterial biomass was used in its native and non-pretreated state, unlike the dried, freeze-dried or chemically treated biomass. The biosorption followed pseudo-second-order kinetics and isotherm fitted well to the Langmuir model. Maximum Pb(II) biosorption was observed at 1.7 × 1016 CFU/mL. Influence of Pb(II) on the growth of bacterial biomass was examined by fitting the monod’s model. Specific growth rate and maximum specific growth rate of B. badius AK was observed as 0.05 and 2.54 h−1, respectively; biomass yield coefficient was 11.81. The results indicated that bacterial biomass was efficient, robust and cheaper biosorbent for removal of Pb(II). GRAPHICAL ABSTRACT

Optimization and effect of dairy industrial waste as media components in the production of hyaluronic acid by Streptococcus thermophilus

ABSTRACT Hyaluronic acid (HA) production using a dairy industrial waste is a more cost-efficient strategy than using an expensive synthetic medium. In this study, we investigated the production of HA using Streptococcus thermophilus under shake flask conditions using dairy industrial waste as nutritional supplements, namely whey permeate (WP) and whey protein hydrolysate (WPH). Preliminary screening using Plackett–Burman design exhibited WP, WPH, initial pH, and inoculum size as significant factors influencing HA titer. Response surface methodology design of four factors was formulated at three levels for enhanced production of HA. Shake flask HA fermentation by S. thermophilus was performed under global optimized process conditions and the optimal HA titer (342.93 mg L−1) corroborates with Box–Behnken design prediction. The molecular weight of HA was elucidated as 9.22–9.46 kDa. The ultralow-molecular weight HA reported in this study has a potential role in drug and gene delivery applications.