Journal of Mechanical Engineering Science and Technology ISSN 2580-0817 Vol. 6, No. 1, July 2022, pp. 34-39 34 DOI: 10.17977/um016v6i12022p034 Effect of Homogenization Pressure on Bacterial Cellulose Membrane Characteristic Made from Pineapple Peel Waste Muhamad Muhajir1, Heru Suryanto1,2, Yanuar Rohmat Aji Pradana1, Uun Yanuhar3 1Department of Mechanical Engineering, Faculty of Engineering, Universitas Negeri Malang, Jl. Semarang 5, Malang, Indonesia 2Center of Excellence for Cellulose Composite (CECCom), Department of Mechanical Engineering, Universitas Negeri Malang, Jl. Semarang 5, Malang 65145, Indonesia 3Department of Waters resources Management, Faculty of Fisheries and Marine Sciences, Brawijaya University, Jl. Veteran Malang, East Java, Indonesia *Corresponding author:heru.suryanto.ft@um.ac.id Article history: Received: 31 August 2021 / Received in revised form: 8 March 2022 / Accepted: 20 April 2022 ABSTRACT Many studies were conducted to maintain the environment by reducing the waste, especially pineapple peel waste. This study aims to explore the effect of various pressure of the homogenization process on bacterial cellulose membrane surface morphology and structure produced using extract of pineapple peel waste. The methods include the preparation of pellicle samples from the product of the fermentation process of Acetobacter xylinum using a medium from the extract of pineapple peel waste. Bacterial cellulose pellicles were crushed using a blender. Mashed bacterial cellulose pellicle was homogenized in High-Pressure Homogenizer with pressure variation of 150 bar, 300 bar, 450 bar, dan 600 bar and then cast into a mold. The bacterial cellulose solutions were dried in an oven at 60°C for 8 hours. The dried bacterial cellulose membrane was analyzed using XRD for the structure and SEM analysis for the morphology. The results indicate that the crystalline properties of BCM were shifted after being treated by various pressure processing in a High-Pressure Homogenizer. It was found that the High-Pressure Homogenizer with higher pressure reduced the peak intensity, decreased crystalline index from 87% to 70%, and decreased the degree of crystalline from 88% to 77% without changing the cellulose structure. The higher pressure of the homogenization process causes the porosity of the membrane to be decreased. Copyright © 2022. Journal of Mechanical Engineering Science and Technology. Keywords: Bacterial cellulose, high-pressure homogenizer, morphology, pineapple waste, XRD I. Introduction Cellulose is an abundant biopolymer resulted in almost plants. It is composed of many compounds such as lignin, pectin, and hemicellulose, so its need many process and energy to purify plant cellulose. In this case, bacterial cellulose (BC) offers a higher purity source of cellulose than plant cellulose [1]. BC is produced from bacteria secretion in a fermentation medium that acts as a nutrient source, and the most famous bacteria used in the fermentation process for producing BC is Acetobacter xylinum instead of Gluconobacter xylinum [2]. Nowadays, many studies have been conducted to maintain the environment by reducing waste. Agricultural waste has been used as carbon source for many applications. Indonesia is a big product of pineapple till to 200,000 tons per year [4]. Pineapple peels are types of substrates that can be utilized as a carbon source. Thus, it is big opportunities to develop pineapple peel waste as a nitrogen and carbon source [3] to produce BC. Therefore, this ISSN: 2580-0817 Journal of Mechanical Engineering Science and Technology 35 Vol. 6, No. 1, July 2022, pp. 34-39 Muhajir et al. (Effect of of Homogenization Pressure on Bacterial Cellulose Membrane Characteristic) study was conducted to apply pineapple peel waste extract as a medium source in BC production and for the waste's utilization. BC, as natural fibers, has biodegradable properties. It makes BC as one of the favorite materials for various applications. In its natural state, BC has very good properties with a purity of almost 100%. It is getting advantages for getting pure cellulose compared to plant cellulose for future development. The BC structure is constructed of a network of fibrils with a high surface area, making it porous. Its hydrophilic property causes BC has a high water holding capacity. The high purity of BC implied a high crystallinity property causing high mechanical properties [1]. But, BC still has some limitations in the utilization of this biopolymer. So, a composites system was introduced to overcome the limitations of BC. By composting the BC, it can get advantages functions such as; photocatalyst, optical, anti- bacterial, anti-fungal, bio-regeneration, and conductivity properties [5]. In this case, nanoparticles are a way to make nanocomposites by dispersion methods and BC regeneration. A regeneration method is needed to disintegrate BC fibers into nano-size. High Pressure Homogenizer (HPH) is a method to fibrillate BC into nanosized. HPH promotes traditional non-thermal processes for emulsion stabilization and improves color uniformity, viscosity, taste, and texture in the food industry [6]. HPH has been applied for the treatment of micro-fibrillated cellulose suspensions in cellulose [7][8], pulp, and bagasse [9]. It was reported that the HPH process was applied in the isolation of cellulose nanofibers to reduce the diameter of the nanofibers from 117 to 67 nm through crushing force, shear stress, and cavitation [10][11] Furthermore, ease of upgrading and continuous operation are benefit of the HPH process. The problem of homogenizer clogging, which occurs cause of the higher fiber diameter, can be suppressed either by increasing the number of cycles or the pressure in the HPH process. Mechanisms of cavitation, friction, shear, turbulence, rapid pressure drop, velocity, compression, and heat initiate the HPH process [12]. Its process is free from organic solvent and has highly efficiency. Repeatedly application of HPH with pressure treatment can produce high cellulose nanofibers and high fibrillation rates [13][14]. HPH leads to increased entanglements because of nanoformation in the networks structures [15]. HPH processes on BC reduce dimensions from microscales to nanoscales [16]. Microstructural information is needed in engineering BC film to find out the film structure relationship to mechanical properties and parameters in expansion, water release, and water absorption. This study purposed for analyzing the influence of the pressure in HPH process on the characteristics of the BC membrane (BCM). II. Material and Methods Materials The BCM synthesis applied bacteria species of Acetobacter xylinum (Microbiology Laboratory, UM, Malang, Indonesia). The main medium for the fermentation process used an extract of pineapple peels. Chemical reagents such as glucose (C6H12O6), distilled water (H2O), sodium hydroxide (NaOH), ammonium sulfate (NH4)2SO4, and acetic acid (CH3COOH) were used in technical grade [6]. Synthesis of BC BC production was conducted according to previously published methods [17]. 5 kg pineapple peel waste was blended and then filtered to get the extract. 10 L of water was 36 Journal of Mechanical Engineering Science and Technology ISSN 2580-0817 Vol. 6, No. 1, July 2022, pp. 34-39 Muhajir et al. (Effect of of Homogenization Pressure on Bacterial Cellulose Membrane Characteristic) added into a container and boiled on hot plate equipment. Ammonium sulfate 0.5% (w/v) and sugar 10% (w/v) were added into suspension and adjusted the pH using acetic acid until about pH 4.5. The boiled medium was then cooled until room temperature. A.xylinum 10% (v/v) was added to the culture medium, and after 10 days pellicle was then floated on the medium and then harvested. Pellicle boiled in a sodium hydroxide (NaOH)1% at 90C for an hour, then rinsed with water until neutral. Synthesis of BCM The cleaned pellicle was crushed using a high-speed blender. Water as much as 750 ml was added into suspension of 250 ml, then suspensions were inputted into HPH, then the homogenization process was conducted at a pressure of 0 bar, 150 bar, 300 bar, 450 bar, and 600 bar at 5 cycles. The BC solution from HPH was cast into a mold and dried in an oven at 60°C for 8 hr. BCM was saved in a dry box. Morphological observation Observation of the surface morphology of BCM was conducted under SEM, FEI, Inspect-S50. Before observation, specimens were coated using a gold coater (SC7-620 Emitech). Structure Analysis The structure of BCM includes the degree of crystallinity, and crystalline index was conducted using XRD (PanAnalytical, X-Pert Pro). Cu-Kα radiation is used at λ=1.54 Å, at 30 mA and 40 kV. Scanning was conducted in the 2θ range from 10° to 40°. The degree of crystallinity (%Cr) and crystallinity index (CrI) were calculated using Segal’s equation. III. Results and Discussions Morphology analysis The morphology of BCM before and after HPH treatment with various pressures (0 bar, 150 bar, 300 bar, 450 bar, and 600 bar) are shown in Figure 1. The membrane shows a change in pore size to nanometers, and the cellulose fibers are clearly split and peel off into nano-sized particles with increasing pressure in the HPH process. Figure 1a, BCM with HPH pressure of 0 bar shows the highest amount of porosity and the fibers are still not completely split. Figure 1b of BCM with HPH pressure of 150 bar shows that the fibers begin to split and peel to form particles to fill the pores between the random fiber structures of BC. Figure 1c BCM treated with HPH pressure of 300 bar showed reduced porosity compared to Figures 1a and b. However, the BC fibers were still not fragmented and completely exfoliated. Figures 1d and 1e, BCM with HPH pressures of 450 and 600 bar show the least amount of porosity. Even with increasing pressure treatment in HPH processes, the BC fibers completely disintegrate into uniform particles. BCM structure analysis The form of diffractogram of HPH treatment with cycle and pressure variations (150 bar, 300 bar, 450 bar, and 600 bar) is presented in Figure 2. Diffractograms of BCM before and after HPH treatment using various pressures results in crystallinity degree, crystallinity index, 2θ angle, peak height, and crystal size are presented in Table 1. ISSN: 2580-0817 Journal of Mechanical Engineering Science and Technology 37 Vol. 6, No. 1, July 2022, pp. 34-39 Muhajir et al. (Effect of of Homogenization Pressure on Bacterial Cellulose Membrane Characteristic) Fig. 1. Surface morphology of BC membrane: (a) HPH 0 bar, (b) HPH 150 bar, (c) HPH 300 bar, (d) HPH 450 bar, dan (e) HPH 600 bar Fig. 2. Diffractogram of BCM produced by various HPH pressure Table 1 shows the 2θ angle (a1) is between 14.27°–14.33°. 2θ angle (b2) is between 16.45°–16.83°, 2θ angle (c3) is between 22.45°–22.45°. The lowest peak intensity value (a1) is 116.62, and the highest value is 244.82. The lowest peak intensity value (b2) is 76.76, and the highest value is 115.42. The lowest peak intensity value (c3) is 196.81, and the highest value is 439.41. The lowest crystallinity index value is 62%, and the highest value is 87%. 38 Journal of Mechanical Engineering Science and Technology ISSN 2580-0817 Vol. 6, No. 1, July 2022, pp. 34-39 Muhajir et al. (Effect of of Homogenization Pressure on Bacterial Cellulose Membrane Characteristic) The value of the lowest degree of crystallinity is 72% and the highest value is 88%. The lowest crystal size value is 4.76 nm, and the highest value is 5 nm. Table 1. Parameter of BCM resulted from XRD analysis Parameter High Pressure Homogenizer (HPH) Pressure (Bar) 0 150 300 450 600 2θ degree a1 14.27 14.23 14.09 14.33 14.27 b2 16.45 16.47 16.35 16.83 16.49 c3 22.45 22.43 22.45 22.45 22.45 Peak Intensity a1 244.82 213.97 116.62 118.87 120.72 b2 115.42 107.83 76.76 76.83 90.46 c3 439.41 391.47 196.81 201.71 213.16 Crystalline Index (CI%) 87 84 62 70 70 Degree of Crystalline (% Cr) 88 86 72 77 77 IV. Conclusions The present study reports the influences of HPH pressure on BCM properties. After different pressure of the HPH process, BCM was prepared. After HPH treatment with various pressure, the HPH with higher pressure cause a reduction in the peak intensity, then the crystalline index decreases from 87% to 70%, and also degree of crystalline decreases from 88% to 77% without raising a new peak in diffractogram. In the future, the engineered BCM could be developed into many applications in fields of engineering such as membrane filter, membrane separator in battery, sensor, active paper, etc. Acknowledgment A great appreciation was delivered to the DRPM Dikti for the grant of Penelitian Kompetitif Nasional, Fundamental Research with contract no. 8.3.13/UN32.14.1/LT/2021. References [1] K. Qiu and A. N. Netravali, “A Review of Fabrication and Applications of Bacterial Cellulose Based Nanocomposites,” Polym. Rev., vol. 54, no. 4, pp. 598–626, Oct. 2014, doi: 10.1080/15583724.2014.896018. [2] P. R. Chawla, I. B. Bajaj, S. A. Survase, and R. S. Singhal, “Microbial Cellulose: Fermentative Production and Applications,” p. 18, 2009. [3] A. Retegi, N. Gabilondo, C. Peña, R. Zuluaga, C. Castro, P. Gañan, K. de la Caba, and I. Mondragon, “Bacterial cellulose films with controlled microstructure- mechanical property relationships,” Cellulose, vol. 17, no. 3, pp. 661–669, 2010, doi: 10.1007/s10570-009-9389-7. [4] Katadata, “Nanas Jadi Komoditas Buah Unggulan dengan Volume Ekspor Tertinggi | Databoks,” 2020. https://databoks.katadata.co.id/datapublish/2021/03/12/nanas- jadi-komoditas-buah-unggulan-dengan-volume-ekspor-tertinggi (accessed Nov. 12, 2021). [5] N. Shah, M. Ul-islam, W. Ahmad, and J. Kon, “Overview of bacterial cellulose ISSN: 2580-0817 Journal of Mechanical Engineering Science and Technology 39 Vol. 6, No. 1, July 2022, pp. 34-39 Muhajir et al. (Effect of of Homogenization Pressure on Bacterial Cellulose Membrane Characteristic) composites : A multipurpose advanced material,” Carbohydr. Polym., vol. 98, no. 2, pp. 1585–1598, 2013, doi: 10.1016/j.carbpol.2013.08.018. [6] M. Le Troedec, D. Sedan, C. Peyratout, J. P. Bonnet, A. Smith, R. Guinebretiere, V. Gloaguen, P. Krausz, “Influence of various chemical treatments on the composition and structure of hemp fibres,” Compos. Part A Appl. Sci. Manuf., vol. 39, no. 3, pp. 514–522, Mar. 2008, doi: 10.1016/j.compositesa.2007.12.001. [7] L. Y. Mwaikambo, “Tensile properties of alkalised jute fibres,” BioResources, vol. 4, no. 2, pp. 566–588, 2009, doi: 10.15376/biores.4.2.566-588. [8] N. Reddy and Y. Yang, “Preparation and Characterization of Long Natural Cellulose Fibers from Wheat Straw,” J. Agric. Food Chem., vol. 55, no. 21, pp. 8570–8575, Oct. 2007, doi: 10.1021/jf071470g. [9] V. S. Sreenivasan, S. Somasundaram, D. Ravindran, V. Manikandan, and R. Narayanasamy, “Microstructural , physico-chemical and mechanical characterisation of Sansevieria cylindrica fibres – An exploratory investigation,” Mater. Des., vol. 32, no. 1, pp. 453–461, 2011, doi: 10.1016/j.matdes.2010.06.004. [10] M. Jacob, B. Francis, and S. Thomas, “Dynamical Mechanical Analysis of Sisal / Oil Palm Hybrid Fiber-Reinforced Natural Rubber Composites,” Polym. Compos., pp. 671–680, 2006, doi: 10.1002/pc. [11] N. Reddy and Y. Yang, “Structure and Properties of Natural Cellulose Fibers Obtained from Sorghum Leaves and Stems,” J. Agric. Food Chem., vol. 55, pp. 5569– 5574, 2007. [12] L. L. A. Koh, J. Chandrapala, B. Zisu, G. J. O. Martin, S. E. Kentish, and M. Ashokkumar, “A comparison of the effectiveness of sonication, high shear mixing and homogenisation on improving the heat stability of whey protein solutions,” Food Bioprocess Technol., vol. 7, no. 2, pp. 556–566, 2013, doi: 10.1007/s11947-013- 1072-1. [13] J. Li, X. Wei, Q. Wang, J. Chen, G. Chang, L. Kong, J. Su, and Y. Liu, “Homogeneous isolation of nanocellulose from sugarcane bagasse by high pressure homogenization,” Carbohydr. Polym., vol. 90, no. March 2016, pp. 1609–1613, 2012, doi: 10.1016/j.carbpol.2012.07.038. [14] I. Hongrattanavichit and D. Aht-ong, “Nanofibrillation and Characterization of Sugarcane Bagasse Agro-Waste Using Water-Based Steam Explosion and High- Pressure Homogenization,” J. Clean. Prod., vol. 277, p. 123471, 2020, doi: 10.1016/j.jclepro.2020.123471. [15] S. Ang, V. Haritos, and W. Batchelor, “Effect of refining and homogenization on nanocellulose fiber development, sheet strength and energy consumption,” Cellulose, vol. 26, no. 8, pp. 4767–4786, 2019, doi: 10.1007/s10570-019-02400-5. [16] N. Kawee, N. T. Lam, and P. Sukyai, “Homogenous isolation of individualized bacterial nanofibrillated cellulose by high-pressure homogenization,” Carbohydr. Polym., vol. 179, pp. 394–401, Jan. 2018, doi: 10.1016/j.carbpol.2017.09.101. [17] H. Suryanto, T. A. Sutrisno, M. Muhajir, N. Zakia, and U. Yanuhar, “Effect of peroxide treatment on the structure and transparency of bacterial cellulose film,” in MATEC Web of Conferences, 2018, vol. 204, doi: 10.1051/matecconf/201820405015.