Team:Edinburgh OG/Scaling Up

 

 

 

 

 

Scaling Up of PHBV Production

PHBV Production Simulation in Industrial Scale using SuperPro Designer

Overview

Life cycle assessment (LCA) has the capacity of pinpointing the hotspots in a system to allow its improvement with a more sustainable outlook which will definitely benefit the environment as well as the current and future generations. This year, the University of Edinburgh Overgraduate iGEM team engineered PHA production pathway in E. coli. And in this project, LCA analysis was conducted to analyses sustainability of industrial scale PHA production, helping to understand the implication of using a whisky by-product as the feedstock in the production as well as its impact upon the environment.

Background

Since five decades ago, computer simulation models have been extensively used in order to investigate economical and physical implications from experimental alterations, to facilitate in both plant design and business plan. From numerous simulation software available, SuperPro Designer v9.5(Academic Site Edition) (Intelligen Inc.) was chosen to be used here as it is a comprehensive process simulator that supports modelling, evaluation, and optimisation of various pharmaceutical, chemical, food and related processes. Process simulator is a crucial tool and has been used widely especially in the Bioprocess Engineering field. Considering there is limited information regarding industrial scale PHBV production available, we decided to simulate PHBV production that incorporate PHA synthesis pathway that we personally engineered in this project.

Aims

We aim to analyse sustainability of industrial scale PHBV production by simulating the process in SuperPro Designer. The result obtained from this was fed into our Life Cycle Assessment.

Materials and Methods

PHBV production was simulated from the pre-treatment stage of the whisky by-product (pot ale) to the recovery stage using SuperPro Designer v9.5 (Academic Site Edition). Prior to any simulation, batch process operating mode was selected with default annual operating time of 7920.0 h. All components used were registered under Pure Components (such as sodium chloride and carbon dioxide) or Stock Mixture (such as ethanol (10% (v/v)). Unit operations and its respective parameters involved were added and connected with one another to construct the complete simulation setup. The selected unit operations are adapted from various literatures as listed in Table 1.

Table 1 List of unit operations utilised in the PHBV production simulation using Superpro Designer

Unit Operations

References

Pre-treatment Stage

Sterilisation

Rodriguez-Perez et al. (2018)

Enzymatic hydrolysis

Tokuda et al. (1998)

Centrifugation

Fermentation Stage

Fermentation

Srirangan et al. (2016), Bothfeld et al. (2017), Shehata and Marr (1971)

Recovery Stage

NaOH treatment

Choi and Lee (1999), Anis et al. (2013)

Centrifugation

Washing using ethanol

Drum Drying

Van Wegen, Ling and Middelberg (1998)

Results and Discussion

PHBV production was simulated at a smaller scale (1 L or lab scale) and then upscaled gradually through pilot to an industrial scale. And in this study, the adjustments considered were substrate feeding substrate feeding style, time, and the recovery method.

Figure 1 1,000 L scale PHBV production simulation and mass balance

The complete the mass balance of each unit operation is shown in Table 2. One batch of PHBV production using 1,000 L working volume resulted in 42.06 kg PHBV with 94.93% purity and 91.48% recovery yield. The entire system required 8.79 days to complete.

Table 2 Mass Balance of PHBV production in 1,000 L working volume scale

Input

Output

Detail

Amount

Detail

Amount

Pre-treatment (includes sterilisation and enzymatic hydrolysis)

Untreated pot ale

28,223.30 kg

Treated pot ale

28,504.07 kg

Enzyme

280.52 kg

Steam

598.78 kg

Water – CIP

5,412.19 kg

Waste water

50,382.74 kg

Steam – sterilisation

598.78 kg

 

 

Cooling water – heat transfer agent

44,970.55 kg

 

 

Glucose Recovery (centrifugation)

Treated pot ale

28,504.07 kg

Concentrated pot ale

624.93 kg

Water – CIP

4,476.17 kg

Waste water

32,355.31 kg

Seed culture (fermentation)

Media

2.56 kg

Biomass

3.49 kg

Inoculum

0.99 kg

Gas emission

5.34 kg

Ammonia

1 kg

Waste Water

219.34 kg

Air

4.26 kg

Steam – SIP

0.22 kg

Water – CIP

201.97 kg

 

 

Steam – SIP

0.22 kg

 

 

Chilled water – heat transfer agent

17.37 kg

 

 

PHBV production (fermentation)

Media – pot ale

454.55 kg

PHBV slurry

1,000.33 kg

Fed media – concentrated pot ale

624.93 kg

Gas emission

1,779.25 kg

Biomass

3.49 kg

Waste Water

21,378.61 kg

Ammonia

25.00 kg

 

 

Air

1670.16 kg

 

 

Water – CIP

1,328.12 kg

 

 

Chilled water – heat transfer agent

20,050.49 kg  

 

 

PHBV recovery (NaOH treatment)

PHBV slurry

1,000.33 kg

PHBV treated slurry

3,444.81 kg

NaOH

9.78 kg

Waste Water

1,492.06 kg

Water – NaOH dissolvent

2,434.70 kg

 

 

Water – CIP

1,492.06 kg

 

 

PHBV recovery (centrifugation)

PHBV treated slurry

3,444.81 kg

Solid stream – PHBV

273.58 kg

Water – CIP

1,492.06 kg

Waste Water

4,663.29 kg

Washing (ethanol treatment)

Solid stream – PHBV

273.58 kg

Washed PHBV

271.29 kg

Ethanol

37.78 kg

Waste Water

1,683.25 kg

Water – ethanol mixture

151.12 kg

 

 

Water – CIP

1,492.06 kg

 

 

Drum drying

Washed PHBV

271.29 kg

PHBV

42.06 kg

Steam

458.45 kg

Gas emission

229.22 kg

Water – CIP

1,492.06 kg

Waste Water

1,492.06 kg

 

Future work

The simulation had provided insights into the efficiency of the proposed process. This will certainly need to be further optimized before being implemented in large scale.  

References

  • SuperPro Designer® [Internet]. Available from: http://www.intelligen.com/superpro_overview.shtml
  • Rodriguez-Perez, S., Serrano, A., Pantión, A.A. and Alonso-Fariñas, B., 2018. Challenges of scaling-up PHA production from waste streams. A review. Journal of environmental management205, pp.215-230.
  • Tokuda, M., Ohta, N., Morimura, S. and Kida, K., 1998. Methane fermentation of pot ale from a whisky distillery after enzymatic or microbial treatment. Journal of fermentation and bioengineering85(5), pp.495-501.
  • Srirangan, K., Liu, X., Tran, T.T., Charles, T.C., Moo-Young, M. and Chou, C.P., 2016. Engineering of Escherichia coli for direct and modulated biosynthesis of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer using unrelated carbon sources. Scientific reports6, p.36470.
  • Bothfeld, W., Kapov, G. and Tyo, K.E., 2017. A glucose-sensing toggle switch for autonomous, high productivity genetic control. ACS synthetic biology6(7), pp.1296-1304.
  • Shehata, T.E. and Marr, A.G., 1971. Effect of nutrient concentration on the growth of Escherichia coliJournal of Bacteriology107(1), pp.210-216.
  • Choi, J.I. and Lee, S.Y., 1999. Efficient and economical recovery of poly (3‐hydroxybutyrate) from recombinant Escherichia coli by simple digestion with chemicals. Biotechnology and bioengineering62(5), pp.546-553.
  • Anis, S.N.S., Iqbal, N.M., Kumar, S. and Al-Ashraf, A., 2013. Increased recovery and improved purity of PHA from recombinant Cupriavidus necatorBioengineered4(2), pp.115-118.
  • Van Wegen, R.J., Ling, Y. and Middelberg, A.P.J., 1998. Industrial production of polyhydroxyalkanoates using Escherichia coli: An economic analysis. Chemical Engineering Research and Design76(3), pp.417-426.