a preliminary study on upscale through biomass …

www.wjpr.net Vol 7, Issue 7, 2018.

303

Sumitha. World Journal of Pharmaceutical Research

A PRELIMINARY STUDY ON UPSCALE THROUGH BIOMASS

PREPARATION AND IMMOBILISATION OF BREVIBACTERIUM

HELVOLUM FOR LABORATORY SET UP OF BIO-

DECAFFEINATION.

Sumitha J.*

Assistant Professor, Department of Microbiology, JBAS College for Women, Chennai.

ABSTRACT

Whole-cell immobilization is a tool to intensify microbiological pro-

cesses. Several examples of production of a variety of biochemical by

immobilized cells have been successfully demonstrated. Though ini-

tially our knowledge on physiology of immobilized cells was limited

and hypothetical, the use of microelectrodes and development of non-

invasive techniques to study the immobilized cells under microenvi-

ronment have revealed significant information pertaining to metabolic

structural alterations occurring in the cell under immobilized phase.

Though a variety of carrier materials have been tried, there are very

few reports comparing these in terms of their performance, long-term

stability and cost. The observations made with immobilized cells and altered morphology in-

dicates the influence of anchorage on cell me tabolism. Except for a few experimental ven-

tures, most of the experiments have been carried out on a very small scale, and hence very

difficult to scale up. The present work focusses around not only for developing feasible mi-

crobiological processes with immobilized cells but also for carrying out extensive research in

design in bioreactor for bio-decaffeination to solve some of the problems, especially the ones

that are connected with diffusional limitations.

KEYWORDS: Biodecaffeination, Immobilisation, Brevibacterium Helvolum.

INTRODUCTION

Biodecaffeination of tea, coffee and other caffeine containing materials is gaining importance

due to the increasing demand for the decaffeinated products and the consumer preference to-

World Journal of Pharmaceutical Research SJIF Impact Factor 8.074

Volume 7, Issue 7, 303-316. Conference Article ISSN 2277– 7105

*Corresponding Author

Sumitha J.

Assistant Professor,

Department of Microbiology,

JBAS College for Women,

Chennai.

Article Received on

12 Feb. 2018,

Revised on 05 March 2018,

Accepted on 26 March 2018

DOI: 10.20959/wjpr20187-11617

8533


304


wards naturally biodecaffeinated products. Development of biodecaffeination processes for

caffeine containing materials requires the employment of microorganisms or enzymes capa-

ble of degrading caffeine. Immobilized cells have advantages over free cells due to the reten-

tion of the cells in the matrix enabling reuse of the immobilized cells and multi enzymes in-

volved in sequential degradation of caffeine to NH3 and CO2. The conversion of caffeine to

its metabolites is primarily brought about by N-demethylases (such as caffeine

1Ndemethylase and 3N-demethylase), xanthine oxidase, uricase, urease etc., that are pro-

duced by several caffeine-degrading bacterial species such as Pseudomonas putida, Serratia,

Alcaligenes, Rhodococcus, Klebsiella, etc. Development of biodecaffeination techniques us-

ing whole cells offers an attractive alternative to the present existing chemical and physical

methods removal of caffeine, which are costly,toxic and non-specific to caffeine.

The technique used for the physical or chemical fixation of cells, organelles, enzymes, or

other proteins (e.g. antibodies), Nucleic acids (DNA, RNA) onto a solid support, into a solid

matrix or retained by a membrane, in order to increase their stability and make possible their

repeated or continued use making the process economical.The industrial biotechnology pro-

cesses using microorganisms generally involve the cells suspended in the fermentation medi-

um. The classical fermentations suffer from various constrains such as low cell density, nutri-

tional limitations, and batch-mode operations requiring high power input. It has been well

recognized that the microbial cell density is of prime importance to attain higher volumetric

productivities. The continuous fermentations with free-cells and cell recycle options aim to

enhance the cell population inside the fermentor.

During the last 20–25 years,the cell immobilization technology, with its origins in enzyme

immobilization,eliminates most of the constrains faced with free- cell systems and has at-

tracted the attention of several research groups. The remarkable advantage of immobilized

cell based system is the freedom it has to determine the cell density prior to fermentation.It

also facilitates operation of microbial fermentation on continuous mode without cell washout.

Since the early 70s, when Chibata’s group (Chibata et.al., 1974 a&b) announced successful

operation of continuous fermentation of l-aspartic acid, numerous research groups have at-

tempted various microbial fermentations with immobilized cells. Several process based on

immobilized microbial cells have been developed.


305


Rationale For Whole Cell Immobilisation

Immobilization commonly is accomplished using a high molecular hydrophilic polymeric gel

such as alginate, carrageenan, agarose, etc. In these cases, the cells are immobilized by en-

trapment in the pertinent gel by a drop-forming procedure. The major factors which deter-

mine the applicability of an immobilized cell based bioprocess include cost of immobiliza-

tion, mass transport limitations, applicability to a specific end-product, etc. These factors are

to be carefully examined before choosing any particular methodology. Many processes have

been practised traditionally, embodying the basic principle of microbial conversions offered

by cells bound to surfaces. Some examples of use of immobilized cells include waste treat-

ment in trickling filters and ethanol oxidation to produce vinegar. Immobilization of cells is

the attachment of cells or their inclusion in distinct solid phase that permits exchange of sub-

strates, products, inhibitors, etc., but at the same time separates the catalytic cell biomass

from the bulk phase containing substrates and products. Therefore it is expected that the mi-

croenvironment surrounding the immobilized cells is not necessarily the same experienced by

their free-cell counterparts.

Immobilisation Methods

Many methods namely adsorption, covalent bonding, cross-linking, entrapment, and encapsu-

lation are widely used for immobilization (Groboillot, et.al.1994). Every method has its own

advantages and disadvantages and the immobilization method varies from process to process.

Immobilisation Matrices

Immobilization matrices must prevent the bacteria from dislodging from the matrix and flow-

ing downstream. An ideal immobilization matrix would be functional at ambient tempera-

tures, survive harsh wastewater conditions including contaminated water and turbidity, and

allow the flow of nutrients and oxygen and analytes through the matrix along with wastes out.

It would also prevent cell flow within the matrix. There are several types of immobilization

matrices used for whole cells studied today.

Modified Methods Of Cell Immobilization

Entrapment of microbial cells within the polymeric matrices is preferred by many research-

ers. Among the various methods, alginate gels have received maximum attention. There are

several studies on the composition of alginate and their suitability for cell immobilization

(Nguyen and Luong, 1986; Kurosawa et al., 1989; Mignot, and Junter, 1990). Studies on the

diffusional characteristics of the immobilized system are being carried out to provide a better


306


understanding on the microenvironment prevailing near the immobilized cells (Axelsson, et.

al, 1994;Westrin, 1990; Willaert, and Baron, 1994; Teixeira, et.al., 1994; Jamuna et.al.,

1992;Ogbonna et.al., 1989; Vorlop, and Klein, 1981) which will enable researchers to opti-

mize the immobilization protocols (Nishida et.al., 1977; Takata et.al., 1978) and to improve

the stability of the gel beads by modifying the protocols like hardening the beads by glutaral-

dehyde treatment (Ruggeri et.al., 1991; Yamagiwa et.al., 1993).

Incorporation of additional component into the gel matrix to improve the mechanical strength

has been tried. Several components such as silica (Chu et.al.,1995), sand, alumina, and vari-

ous gums are generally used. In addition, the gel particles are further strengthened by treating

with various cross-linking agents, such as glutaraldehyde. Chu et al. (1995) reported the

polyelectrolyte complex gel prepared from xanthan and chitosan for immobilization of

Corynebacterium glutamicum having fumarase activity. By mixing two opposite-charged

electrolytes, a complex resulted due to electrostatic interactions. Generally, these complexes

were obtained as precipitates, but Sakiyama et al (1993) and Chu et al. (1995) obtained

moldable chitosan/ k -carrageenan and xanthan/chitosan complex gels in the presence of

NaCl. It has been observed that the cells immobilized in these complexes were very stable

and exhibited 5-fold higher activity compared to free- cells. The pore size was found to be

similar to that of polysaccharide gel. In a similar study, Pandya and Knorr (1991) used low

molecular weight compounds which were immobilized in complex coacervate capsules con-

sisting of water-soluble chitosan salts or acidsoluble chitosan cross-linked with k -

carrageenan or alginate. This type of coacervatre capsules could be used for cell immobiliza-

tion and simultaneously the presence of chitosan salts in the capsule will affect permeabiliza-

tion of the cells.

Emerging Trends

Whole-cell immobilization as a tool to intensify microbiological processes has been well es-

tablished. Several examples of production of a variety of biochemicals by immobilized cells

have been successfully demonstrated. Though initially our knowledge on physiology of im-

mobilized cells was limited and hypothetical, the use of microelectrodes and development of

noninvasive techniques to study the immobilized cells under microenvironment have revealed

significant information pertaining to metabolic structural alterations occurring in the cell un-

der immobilized phase. Though a variety of carrier materials have been tried, there are very

few reports comparing these in terms of their performance, long-term stability, and cost. The


307


observations made with immobilized cells and altered morphology indicate the influence of

anchorage on cell metabolism. An important area of research requiring greater focus is the

bioreactor design and its long-term operation. Except for a couple of experimental ventures,

most of the experiments have been carried out on a very small scale, and hence very difficult

to scale up. The future research should centre around not only for developing feasible micro-

biological processes with immobilized cells but also for carrying out extensive research in

bioreacter design to solve some of the engineering problems, specially the ones that are con-

nected with diffusional limitations.

Application of Immobilized Cells for Bio- Decaffeination

Caffeine is an alkaloid naturally occurring in coffee, cocoa beans, cola nuts and tea leaves,

and is a central nervous system stimulant. It is known to show toxicity when fed in excess

and is even mutagenic in-vitro (Friedman and Waller, 1983a and b). Excessive consumption

of caffeine through beverages is associated with a number of health problems (Friedman and

Waller, 1983a and b, Srisuphan and Bracken, 1986, Dlugosz et.al., 1996). Increasing

knowledge of the effects of caffeine on human health led to the development of processes for

decaffeination using solvents which are considered unsafe for humans. Biotechnological

means of decaffeination have been considered as safe alternatives for the conventional decaf-

feination processes. Since 1970’s several studies have been conducted by several groups in

the world on the identification of caffeine degrading organisms for possible use in the devel-

opment of biodecaffeination technologies.

Caffeine degrading bacteria and fungi have immense potential in the decaffeination processes

for utilization of coffee, tea and other caffeine containing wastes which are otherwise unusa-

ble and pose sever health and environmental problems (Roussos, et.al., 1995). Although sev-

eral reports on the use of free cells of bacteria and fungi for the degradation of caffeine are

available, they are limited to solid state fermentation of caffeine containing agro wastes

(Jarquín, 1987). Caffeine is now being determined as a marker for contamination of water

and processes involving decontamination of caffeine laden waste waters have high environ-

mental significance. Literature in this area is scanty. Middelhoven and Beckker- (1982) report

the immobilization of a caffeine-resistant strain of Pseudomonas putida isolated from soil in

agar gel particles which were continuously supplied with a caffeine solution in a homogene-

ously mixed aerated reaction vessel. The caffeine degradation was monitored in this reactor

system. No other reports are available on the immobilization of microbial cells for the degra-


308


dation of caffeine. Caffeine degrading microorganisms utilizing caffeine as the sole source of

carbon and nitrogen have been isolated and characterized which have enzymes that bring

about the actual degradation of the substrate. In this thesis, we report the isolation of an effec-

tive caffeine-degrading microbe Brevibacterium helvolum from soil, its growth and decaf-

feination studies.

MATERIALS AND METHODS

Biomass Production

A loop full of actively growing culture of the isolate from the culture slant was transferred to

100ml of nutrient broth containing 0.3 g.L-1 caffeine and incubated at 30°C in an orbital

shaker for 24 hrs. A 5% v/v of the 24 hrs grown pre inoculum was transferred to 100ml of

nutrient broth containing 0.3 g.L-1 caffeine and grown under the same conditions. Samples

were drawn at known intervals of time for the measurement of cell growth. Biomass accumu-

lated after 24 hours was harvested by centrifugation in a bench top centrifuge (Kubota, Japan)

at 16,000g for 20 min at 0-4° C to form a pellet.

Biomass Determination

The cell pellets after centrifugation of the culture samples were washed twice with deionized

water and O.D 600 nm was measured. For cell dry weight (O.D600 nm of 0.5 corresponds to

0.379 g dry weight /100ml according to standard curve).

Whole cell immobilization- immobilization method


309


Immobilisation of the cell of Brevibacterium helvolum was done by dissolving 3 gm of suita-

ble matrix powder in 100ml of distilled water with subsequent mixing of 10 gm of cell equil-

ibrated to the particular temperature. After thorough mixing, the suspension was dropped

through a syringe into suitable suspending liquid maintained at suitable temperature.

Entrapment method of immobilization of the cell was carried out using different matrices. A

scheme of preparation of immobilized cells of Brevibacterium helvolum is given in scheme

below (V.R.Sarath Babu, 2005):

Immobilization Matrices

Agar As Matrix

Immobilisation of the cell of Brevibacterium helvolum in agar was done by dissolving 3 gm

of agar in 100ml of distilled water 80OC and then cooling it to 40O C with subsequent mix-

ing of 10 gm of cell equilibrated to the same temperature. After thorough mixing, the suspen-

sion was dropped through a syringe into water maintained at 4°C.

Gelatin As Matrix

Gelatin (porcine skin) was used as the matrix for the immobilization of cells of Brevibacte-

rium sp.,. Solutions of gelatin in the concentration range of 3-20% was prepared by dissolv-

ing required weight of solid gelatin powder in 100 ml water maintained at 60OC. Cells of

Brevibacterium (Ten grams by wet weight) were mixed with 100 ml of gelatin maintained at

300C and mixed thoroughly to obtain a homogeneous suspension. This suspension was then

dropped slowly into an aqueous solution of 1.5% v/v glutaraldehyde at 4°C using a surgical

syringe.

κ–carrageenan as matrix

A 3% w/v solution of κ–Carrageenan was prepared by dissolving 3 grams of κ-Carrageenan

in 100ml of distilled water maintained at 600C. The solution was then cooled to 40-45

0C and

10 grams wet weight of cells previously equilibrated to the same temperature was suspended

in the solution. The mixture was maintained at a temperature of 40-450C and mixed thor-

oughly to obtain a homogenous suspension. This suspension was then dropped slowly into an

aqueous solution of 2% KCl at 4°C using a surgical syringe.

Sodium Alginate As Matrix

Sodium alginate solution (3% w/v) and was prepared and sterilized. 10 grams cell by wet

weight was mixed thoroughly in the alginate solution. The cell suspension was dropped slow-


310


ly into a solution of 0.22 M Calcium chloride at 40C. The beads were kept for primary curing

at 0C for 24 hours and secondary curing was done in 0.02 M calcium chloride for 48 hours at

40C. Traces of calcium chloride were removed by through washing with distilled water.

Biodecaffeination Studies By Immobilized Brevibacterium Helvolum By Shake Flask

Experiment: Immobilized cells of Brevibacterium helvolum were tested for the ability to de-

grade caffeine in shake flask. 10 gm of the immobilized beads were incubated with 100 ml of

the working medium under agitation on a rotary shaker set at 200 rpm.

Growth of Cells and Induction for Caffeine Degradation

A loop full of actively growing culture of the isolate from the culture slant was transferred to

100ml of nutrient broth containing 0.3 g.L-1 caffeine and incubated at 300C in an orbital

shaker for 24 hrs. A 5% v/v of the 24 hrs grown pre inoculum was transferred to 100ml of

nutrient broth containing 0.3 g.L-1 caffeine and grown under the same conditions. Samples

were drawn at known intervals of time for the measurement of cell growth. Biomass accumu-

lated after 24 hours was harvested by centrifugation in a bench top centrifuge (Kubota, Japan)

at 16,000g for 20 min at 0-40C to form a pellet.

The biomass pellet was aseptically transferred into a 500ml flask containing 100ml of CLM

containing 1g.L-1 caffeine and incubated at 300C on the orbital shaker for a period of 48hrs

for inducing the cells to degrade caffeine. These induced cells were harvested by centrifuga-

tion as before. The cells were washed several times to remove caffeine. 10 grams of these in-

duced cells were suspended in 100 ml of phosphate buffer containing caffeine, which were

used for caffeine degradation experiments.

Caffeine degradation studies by Brevibacterium helvolum

Induced cell suspension (10 ml) was aseptically transferred to 90ml of CLM containing 1g/l

caffeine and incubated on a rotary shaker at 300C set at 150 rpm for 4hours. 0.5 ml aliquot

samples were drawn at 2, 4, 6, 12 and 24 hours, centrifuged and the supernatants were ana-

lyzed for residual caffeine content. Studies on the effect of pH and temperature on biodecaf-

feination by the isolate were carried out by incubating the induced cells in CLM containing

1g/l caffeine, which was adjusted to different pH and temperature.For studying the effect of

inoculum on caffeine degradation, induced cell suspension was added to CLM containing

1g/l caffeine so as to obtain inoculums levels of 1.2, 2.5, 5.0 and 7.5%w/v (based on wet

weight).


311


Studies on the effect of caffeine concentration on the biodecaffeination efficiency of the iso-

late were carried out by incubating the induced cells in CLM containing caffeine in the con-

centration 152 range of 1-5 g/l. Samples were drawn at known intervals of time and analyzed

for caffeine content.

Optimisation of Parameters For Immobilisation By Brevibacterium helvolum

Effect of temperature on immobilised cells of Brevibacterium helvolum

Immobilized cells of Brevibacterium helvolum were incubated with phosphate buffer contain-

ing 1g.L-1 of caffeine which was adjusted to 18, 28, 32, 48 and 600C in a water bath and in-

cubated for 96 hours and checked for biodecaffeination ability.

Effect of pH on immobilized cells of Brevibacterium helvolum

For maximal caffeine degradation it is important that the working medium should be at an

optimal pH, which would maintain the cells in their viable state, and the enzymes responsible

for decaffeination are highly active. Phosphate buffer at different pH was used for biodecaf-

feination of caffeine solution and the residual caffeine at different pH was recorded.

Effect Of Oxygen Availability On Immobilised Cells of Brevibacterium helvolum

The caffeine-degrading organism being an aerobe needs oxygen for its viability. Further,

some of the enzymes involved in caffeine degradation pathway are also oxygenases necessi-

tating the presence of molecular oxygen in the system. Therefore to check the requirement of

oxygen for efficient degradation of caffeine, experiment was conducted without oxygen

supply.

Effect Of Inoculum Volume On Immobilised Cells Of Brevibacterium helvolum

Cell suspension containing w/v of cells (wet weight) in 3% calcium alginate solution were

prepared and dropped slowly into a 2% calcium chloride solution and cured in the same solu-

tion. The immobilized cells were then incubated with caffeine and their decaffeination ability

was checked.

Caffeine Degradation Studies By Immobilised Brevibacterium helvolum Under Optimal

Conditions

Studies on the effect of pH and temperature on biodecaffeination by the Immobilized cells

were carried out by incubating the induced cells in phosphate buffer containing 1g/l caffeine,

which was adjusted to different pH and temperature.


312


For studying the effect of inoculum on caffeine degradation, immobilized cell was added to

calcium chloride containing 1g/l caffeine so as to obtain inoculums levels of 1.2, 2.5, 5.0 and

7.5%w/v (based on wet weight). Studies on the effect of oxygen availability on the biodecaf-

feination efficiency of the immobilized cells were carried without external oxygen supply.

RESULT AND DISCUSSION

Immobilization of Brevibacterium helvolum in different matrices

Gelatin: Gel formation was achieved by dropping the gelatin- cell suspension into cold wa-

ter. Bead formation was not uniform and tailing of beads was observed. The beads were also

not physically stable. Bead formation by crosslinking with glutaraldehyde was tried. During

bead formation in the curing solution tailing of the beads was observed. The tailing of beads

persisted even when the glutaraldehyde concentration was increased to 5%.

Κ–carrageenan

Induced cells of Brevibacterium helvolum were immobilized in κ- carrageenan . The beads

formed by immobilization in κ–carrageenan were fragile. An initial curing in 20% KCl for 30

minutes at 4oC and subsequent curing at the same temperature in a solution of 2% KCl for 24

hours was found satisfactory. But after the completion of curing and incubation of the beads

with caffeine solution under agitation led to the rapid disintegration of the beads.

Agar: The beads obtained using agar as matrix were soft and not able to withstand pressure

when agitates. Only 12% decaffeination was possible after 96 hrs.

Sodium alginate

Of all the matrices tried sodium alginate was found to be the best in terms of bead uniformity,

bead strength, handling conditions, porosity and caffeine degradation results.

Table 3.1: Percentage of Caffeine Degradation Immobilized in Different Matrices At

Varying Times.


313


Optimization of Parameters for Decaffeination Using Immobilized Cells of Brevibacte-

rium Helvolum in Sodium Alginate Beads

The effect of pH, temperature and cell loading on the biodecaffeination of caffeine solution

by Brevibacterium helvolum was studied and the parameters for optimum biodecaffeination

were optimized.

Effect of Ph on Immobilized Whole Cells for Caffeine Degradation

For maximal caffeine degradation it is important that the working medium should be at an

optimal pH, which would maintain the cells in their viable state, and the enzymes responsible

for biodecaffeination are highly active. Biodecaffeination at lower pH is very low due to the

low activity of the enzymes in the cells. Only 35% decaffeination was possible at pH 5.0 and

increased with increase in pH up to 8.0 indicating that the cells are capable of biodecaffein-

ation at neutral and slightly alkaline conditions. The cells however could biodecaffeinated

only 65% caffeine at pH 9.0. This is due to the higher alkalinity of the medium where the en-

zymes are not active.

Table 3.2.1: Percentage of Caffeine Degradation Immobilized in Different Ph At Vary-

ing Times.

Effect of Temperature on the Immobilization of Whole Cell for Caffeine Degradation

Brevibacterium helvolum is a mesophilic organism and grows best at 30±20C. . Maximum

biodecaffeination was observed at 320C and 48

0C (89.2 and 40% respectively). At these tem-

peratures the cells are metabolically active and degrade maximum caffeine. Temperatures

above this are detrimental to the cells leading to a loss of activity of the enzymes involved in

the biodecaffeination.


314


Table 3.2.2: percentage of caffeine degradation immobilized in Different temperature at

varying times.

Effect of cell loading on the immobilization of whole cell for decaffeination

At low cell concentrations (2 and 4% w/V of cells) only 40-54 % decaffeination was

achieved. This is supposed to be due to the low number of bacterial cells present for degrad-

ing caffeine in the solution. Caffeine being inhibitory to the cells might also be involved in

the lower biodecaffeination levels. Biodecaffeination increased with an increase in the cell

loading up to 10% w/v in the gel. It was found that 10 % w/v of the cells was the best for de-

caffeination and caffeine was almost completely degraded within 80 hrs of incubation. So

10% cell loading was found to be optimum to degrade caffeine.

Table 3.2.3: Percentage of Caffeine Degradation Immobilized in Different Cell Load

Volumes at Varying Times.

CONCLUSION

The work reported in this paper has led to the development of biodecaffeination processes for

coffee. Although several critical factors, which affect the biodecaffeination process, have

been identified and optimized, there is a scope for improvement of the efficiency of this pro-


315


cess. Further studies on isolation and stabilization of caffeine demethylase, cloning and hyper

expression of caffeine demethylase, molecular characterization of the enzyme are to be car-

ried out. Also studies on the scale up of the biodecaffeination process are needed.

In conclusion, this paper deals with the basic studies on the microbiological, enzymological

and biochemical aspects of development of biodecaffeination processes. Several bottlenecks

which were found to hinder the process of biodecaffeination were overcome through a de-

tailed study on the factors influencing the activities of enzymes in biodecaffeination has been

carried out. An enzymatic process for biodecaffeination of coffee has to be developed by us-

ing an immobilized system and a biodecaffeination process for coffee developed by using

soluble enzymes. The biodecaffeinated tea and coffee will have the same taste and aroma

profile and no change in quality was observed. These processes have immense potential in

industries and are being pursued.

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