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. 2025 Jan 25;65(2):741–748. doi: 10.1007/s12088-025-01446-3

Valorization of Coconut Shell and Blue Berries Seed Waste into Enhance Bacterial Enzyme Production: Co-fermentation and Co-cultivation Strategies

Pathan Ahemad Khan 1,#, Tripti Singh 2,#, Basant Lal 3,#, Rajeev Singh 4,#, Asad Syed 5, Meenakshi Verma 6, P K Mishra 1, Ling Shing Wong 7, Irfan Ahmad 8, Neha Srivastava 1,9,✉
PMCID: PMC12246293  PMID: 40655365

Abstract

Broad industrial application makes cellulolytic enzymes always in industrial demand with economic and sustainable production method. Production of cellulase enzymes via solid state fermentation mode using solid waste can resolve enzyme production and solid waste management issue in eco-friendly way. In present investigation, co-fermentation of solid wastes and microbial co-cultivation using potential cellulase producers strains have been applied as promising strategy for enhancement of cellulase at economical scale. Under the optimized bioprocess, co-fermentative substrate ratio of 5:4 of coconut waste (Ccw) and jamun fruits (JFs) gave 16 IU/gds filter paper (FP) activity at 12 h of incubation via bacillus strains in solid state fermentation (SSF). Additionally, at optimum production temperature of 42 °C and pH 6.0, enzyme showed 19 and 21 IU/gds FP activity at 12 h of incubation. Further, using different organic and inorganic sources, enzyme produced 26 IU/gds FP activity at 12 h peptone as nitrogen source. Additionally, at 60% optimum, moisture content, enzyme gave highest 31 IU/gds FP activity, 239 IU/gds, β-glucosidase (BGL) activity and 176 IU/gds endoglucanase (EG) activity in 12 h of incubation of SSF confirms the efficient production of all cellulolytic components of enzyme. The study has prominent scope in economical industrial application of this enzyme with promising waste management for environment sustainability applications.

Keywords: Cellulases, Solid waste, Fermentation, Bacillus sp., Co-culture

Introduction

Enzymes are prime focus of commercial market due to their broad applications and ecofriendly biological origin. Additionally, these can be easily obtained from different biological sources like plants, animals and microorganisms in which microbial enzymes are grabbing main attention. Easier production, extraction, availability and efficiency are the advantageous features of microbial enzymes over the enzymes produced from animal and plants via relatively tedious process [1]. Among popular commercial microbial enzymes, extracellular enzymes are more in demand due to easier release in microbial culture medium, filtration and can be extract via following simpler centrifugation method. Among various extracellular enzymes, cellulolytic enzymes are more popular because of its key role in lignocellulosic biomass (LCB) conversion into sugars for biofuels production applications. These are multicomponent enzyme system consist of mainly endoglucanse (EG), cellobiohydrolysase (CBH) and beta-glucosidase (BGL). These subenzyme components function synergically to break complex polymeric form of cellulose into monomeric simple sugars [2]. The efficiency of enzymes varies depending on the source and origin of the production, using different feedstock on which it produced as well as other necessary bioprocess parameters which contributed significantly to enhance the production and efficiency of the enzymes. Among the different influential parameters, feedstocks on which enzymes are being produced are key governing parameter and generally, LCB are referring as the most profound substrate for cellulolytic enzymes production. Higher cellulose content, easier and perianal availability with renewable nature are the preferable benefits are associated with LCB as feedstock [3]. In addition, LCB covers a huge category of solid waste which needs immediate attention for its logical and ecofriendly management. Moreover, due to high cellulose, these wastes are more suitable source of enzymes production. Crop wastes, food and vegetable wastes are rich in cellulose and plenty availability for its effective valorization in enzymes production. Additionally, in this series, coconut wastes (Ccw) are contributed largely in solid waste issues and is rich in high cellulose content with easier availability. Due to high production, consumption and collection, solid waste management of this biomass are in urgency. Though coconuts produced in ~ 92 countries globally and among these, Indonesia, Philippines and India contributed approximately 75% whereas, Indonesia grabbed first position in coconut production [4]. Additionally, the compositional fraction of coconut (cocoas nucifera) includes 39.31% alpha cellulose, 16.15% hemicelluloses, 29.79% lignin and 38.48% extractives [5]. Apart from this waste, waste seeds of many fruits and vegetables are potential source of carbohydrates, sugars, minerals and other bioactive compounds. Among huge verity food wastes, seeds of jamun fruit (Syzygium cumini) (L.) are source of several bioactive compounds and released in large quantity due to huge utilization of this fruit from value added process industries. Additionally, seeds of jamun fruit (JF) covers 10–47% of the total mass of the fruit and discarded solid cause solid waste pollution issue for the process industries and environment and hence adaptability of this challenge is necessary. In contrast, seeds of JF has value addition property due to its enormous bioactive property. Waste seeds of JF contains nutrient like amino acids, vitamin C, vitamin B complexes (thiamine, riboflavin, folic acid), essential minerals and trace elements (calcium, iron, sodium, magnesium, zinc, phosphorus and ~ 31.62% of carbohydrate which confirms the utility of this waste for fermentation as well as nutrient medium equipment [6, 7]. Considering microbial fermentation for cellulolytic enzyme production, solid state fermentation (SSF) is better option over submerge fermentation (SmF) due to advantageous like use of solid waste as substrate, relatively less amount of water to maintain moisture and ambient as well as ecofriendly operations [8].

Therefore, the goal of the present study was to achieve higher and sustainable production of cellulolytic enzymes via co-fermentation of Ccw and JF seeds under SSF mode using cocultured bacterial species of bacillus spp. Further, for enhancement of cellulolytic enzymes, temperature and pH of the production medium has been optimized with nitrogen sources (Scheme 1).

Scheme 1.

Scheme 1

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Overall strategy to enhance bacterial cellulase production under solid state fermentation mode

Materials and Methods

Resources, Chemicals and Extraction

Samples of feedstock Ccw and JF were collected from local available fruit shop and Ccw were cut into small and fine pieces while JF seeds were separated from the pulp and skin of the fruits. Both samples were washed with tap water followed by double distilled water (DD-H2O) and kept for drying in oven at 55 °C until the complete dryness achieved. Thereafter, the dried biomasses of Ccw were cut into small pieces and make the size of 1.5 to 2.0 mm were maintained through sieve whereas, dried JF seeds were grinded into fine powder using mixer and grinder. Further, the moisture of all dried samples was analyzed using moisture analyzer. In addition the extract liquid of JF seeds were obtained via heating of dried JF seed powder mixing with DD-H2O in 1:1 ratio at 60 °C until volume of the mixture become half. The reduced mixture was extracted through filter paper and pH has been analyzed. The final obtained liquid medium was being used as nutrient media and moisture balance in SSF process.

Microorganism, Inoculum Preparation and Culture Maintains

Two strains of Bacillus sp. name Bacillus clausii (Brand: Immunobasics) and Bacillus coagulans (Brand: Meibotan) have been taken from long storage, expired probiotic juice waste have been selected for this study. Valorization of medical waste like expired probiotic juice and potential efficiency of cellulolytic enzymes production were the main reason for selection of this bacterial population for this studies. Further, from expired probiotic juice both the bacterial species have been grown on the nutrient agar (NA) medium plate at 35 °C in BOD incubator for 24 h of first subculturing cycle followed by its successive three subculturing on nutrient broth (NB) in conical flask on continuous stirring under same conditions. After that, fresh subcultured plates were used as inoculum in SSF medium. Additionally, for storage and maintains purpose, NA slants have been prepared and cultures were maintained in cultures tubes in difference of four weeks. Moreover, 30% glycerol stock solution prepared in DD-H2O has been prepared and store in refrigerator.

Solid State Fermentation for Enzyme Production

Cofermentation of two biomasses of Ccw and JF seeds have been performed under SSF using cultivation of two bacterial cultures bacillus sp. in BOD incubator for different incubation time period from 8, 12, 18, and 24 h at pH 5.0 and temperature 35 °C. Different co-fermentative substrate ratio (5:03, 5:04, 5:06 and 5:08) have been used and studied under SSF of cocultures with 10% inoculation using inoculum spreading method over the solid substrate surface whereas, 10% inoculum of spore suspension contained 107 spores/ml spread in each flask of SSF. Further, nutrient composition and moisture balance have been maintained using JF seeds liquid extract at 50% moisture balance under SSF mode along with optimizing different moisture ratios from 55%, 60% and 65%. Further, the optimum temperature (from 37, 42 and 45 °C) and pH (from 4.5, 6.0, 6.5) for maximum cellulase production has been studied following SSF mode. Additionally, nitrogen of the nutrient medium was also studied using nitrogen sulphate (NS), yeast (Y) and peptone (P) from 0.25%, 0.5% and 1.0% in the SSF medium.

Enzyme Extraction, Assay and Statically Analysis

The produced enzymes after completion of SSF incubation period was extracted through the procedure of mixing the SSF medium with 50 mL of sodium citrate buffer at pH 5.0 in conical flask and kept on continuous agitation at 27 °C upto 30 min. Afterwards, the mixture has been filtered through cotton and obtained liquid was centrifuged at 7000 rpm upto 10 min and the received supernatant was used for enzyme characterization studies. Additionally, for characterization studies of enzymes, filter paper activity (FP) which represents overall activity of cellulase enzymes has been done by Ghosh method (1987). Additionally, the same method of Ghosh has been followed for the analysis of endoglucanase (EG) whereas activity and Kubicek et al. [9] protocol was used for the analysis of BGL enzyme followed by protein analysis using Bradford reagent [10]. All the characterization studies were strictly followed by above mentioned protocols. All the experiments were performed in duplicate manner while the data were statistically determined through standard deviation (SD) method.

Results and Discussion

Impact of Cofermentation and Co-cultivation on Cellulase Production

Production of large amount of agroindustrial residue and their inadequate collection is the main concern raising issue towards severe environmental pollution due to solid waste. Additionally, lack of suitable and advance technology for the effective management of solid waste are also point to immediate attention for quick action. Coconut residues contributed largely in solid waste pollution due to high consumption regularly. Moreover, due to higher cellulose content, this waste has enormous potential for value addition [11]. Additionally, mesocarp of this waste has been confirmed as the potential source of carboxymethyl cellulose and hence has approved as potential substrate for cellulolytic enzymes production. Further, nutrient media composition and moisture content play important role in enzyme production wherein, inclusion of synthetic nutrient medium composition may raise the overall cost of the enzyme production. In contrast, nutrient medium obtained from natural resources can be a potential and economical strategy towards sustainable production low cost development of enzymes [12]. Additionally, the resources which are residues of natural bioresources can keep the process even more simple and economical. Among different available bioresources, seeds of jamun fruit are the potential and enrich source of bioactive compounds. Though, jamun seeds are declared as waste from food process industries and considered as solid waste contributors, being 10–47% part of the total mass of the fruit and bioactivity regarded for strong value addition. Because of enriched properties of bioactive compounds these waste seeds can be used as strong source of nutrient medium and in extracted form, transportation would be easier for microbial growth [13]. Thus, in the present study, jamun seeds aquas extract have been used as potential nutrient media replace with commercial media used for the fermentation process. Additionally, these seeds in solid form have also been used as co-fermentative substrate for cellulolytic enzymes fermentation with coconut waste. In [Fig. 1a], cellulase enzyme production on two different monocultures under optimum concentration of separate substrate have been presented and culture S2 showed highest enzyme production in 18 h in both substrate reflecting 9 IU/gds with substrate Ccw and 8 IU/gds with feedstock JFs at 5 and 3 g of substrate, respectively. Though both bacterial cultures showed separate different performance under monoculture stage, they proliferate higher cellulase production under co-fermentative and co-cultivation stage (Fig. 1b). Showing optimum time period 12 h of enzyme production which was peaked in 5:4 substrate ratio of Ccw:JFs, 16 IU/gds enzyme production was recorded. While in contrast, on increasing or decreasing the substrates ratio in cofermentative stage enzyme production got reduced. Higher substrate amount might be a possible reason for slow metabolism and consequently lower enzyme production. Study of Asiri et al. [14] confirmed that cofermentation and Bacillus sp. are strong contributors in cellulase production enhancement. Similarly, investigation of Liu et al. [15] has explored co-fermentation as impactful strategy to enhance the cellulase production and scarification. The study also confirmed that coferementation of the substrate is a promising potential study to enhanced cellulase production. Additionally, in the study of Lee et al. [16], co-fermentation of recombinant Saccharomyces cerevisiae Yeast Strains have been adopted for hyper secretion of cellulase enzymes. Though studies are being available on cellulase production using coconut waste, nearly no study has been found on exploring jamun waste seed valorization as co-fermentative substrate and its extract as nutrient medium composition in SSF. Therefore, the study presented here has promising approach to enhance cellulase production for commercial applications in biomass based biorefinaries.

Fig. 1.

Fig. 1

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a Solid state fermentation of bacterial cellulase production under monoculture stage using blue berry seeds and coconut waste separately for both cultures. b Co-fermentative cellulase production using bacterial co-cultivation at different co-substrate ratio (Ccw:JFs)

Physicochemical Parameters Investigations for Cellulase Production Enhancement

Number of strategies are being tried to develop low cost production cellulase via sustainable approaches for industrial usage. Among these approaches optimization of production media is the most significant along with bioprocess parameters. Additionally, evaluations of different process parameters are needed to be analyzed for different celluase production every time [17]. Moreover, it has been reported that optimization of production media component and physicochemical process improves the yield of the enzyme. Temperature and pH are driven factors to influence the enzyme production via impacting microbial growth and their sustainability. Optimum temperature supported the rapid and high functional enzymes production [18]. Additionally, an optimized pH provides suitable buffering environment for microbial and other media components to produce higher enzymes. In contrast, range of both parameters temperature and pH beyond the optimum value cause severity in enzyme production such as hampering the microbial growth, substrate and microbial interaction and lower metabolism. Additionally, the molecular structural deformation in enzymes occurs due to adverse impact of temperature whereas, growth of microorganisms are completely retarded [19]. Apart from temperature and pH, in bioprocess media optimization, nitrogen also plays important role to improve the yield and production of the enzymes. Presence of appropriate amount of nitrogen in production media supports protein supplements and microbial growth while its deficient retarded in non-supportive pH range during the enzymes production. Additionally, higher amount of nitrogen affects the metabolism of the microbial growth and reduced the production of the enzymes. Moreover, type of the nitrogen sources like organic and inorganic nitrogen sources will also affects the microbial growth, metabolism and enzymes function [20]. Additionally, it has been anticipated that organic nitrogen sources give better performance than inorganic nitrogen sources, specifically in fermentation process including SSF and SmF [21]. One of the major advantages of SSF includes substrate degradation in aerobically mode in absence of free floating water and hence, moisture balance is only significant factor to maintain nutrient transportation in SSF mode of cellulase production. Along with this, simple bioprocess parameters are governing factors due to SSF advantages like requirement of simple operation, ambient condition process apart from waste solid substrate and lower water consumption. Because of these reasons, SSF is the major contributors in solid waste management of solid organic waste and its effective valorization. The number of available reported studies confirms that different cultivated production media and process parameters have different impact on enzyme production and efficiency [22–24]. Therefore, influence of temperature, pH, nitrogen source and moisture balance have been investigated and the pattern of temperature and pH on enzyme production have been depicted in Fig. 2a, b, respectively. Maximum enzyme production has peaked at 12 h and 42 °C with 19 IU/gds FP activity while above this enzyme production got reduced might be due to non-supportive temperature range Fig. 2a. It noteworthy to mention here that at 37 °C the enzyme showed same activity as reflected at 42 °C which indicated efficiency of enzyme to tolerate temperature range from 37 to 42 °C. This expanded temperature range efficient enzymes are categorized in key interest of the industries using application of these types of enzyme because expanded temperature tolerance does not affect the productivity of the enzyme at mass cultivation stage. Further, the enzyme production showed 21 IU/gds FP activity at pH 6.0 of production time period of 12 h while below and above moderating the pH there was drastic change in enzyme activity might be due to shift in the buffering environment for the sustainability of the microorganism Fig. 2b. Further, behavior of enzyme production has been tested on different nitrogen sources at 0.5% concentration and depicted in Fig. 3a. Though two organic nitrogen sources yeast and peptone applied separately for enzyme production whereas, ammonium sulphate was used as inorganic nitrogen source enzyme peaked in presence of peptone giving 26 IU/gds FP activity in 12 h. However, in presence of yeast enzyme showed highest 24 IU/gds FP activity in 12 h while with ammonium sulphate it is 23 IU/gds FP activity in 12 h. Though, in this study type of nitrogen sources does not have very significant impact on enzyme production, its need to be optimized for getting optimum and highest value for large scale production and application. Further, effect of moisture balance have been also monitored on enzyme production and showed in Fig. 3b which reflected its highest enzyme production value 31 IU/gds FP activity in 18 h at 60% of moisture which might be possibly due to process optimization of above parameters. Additionally, at 12 h of incubation, 30 IU/gds FP activity in 18 h at 60% of moisture while alteration at below and higher moisture range the enzyme production got reduced. Non-suitability of microbes attachment on substrate surface is probable explanation to reduce enzyme activity at higher moisture balance than optimum one while below moisture level than optimized value might cause difficulty in nutrient circulation while the course of enzyme production via SSF mode. Optimization of temperature, pH, nitrogen and moisture is crucial for receiving maximum cellulase production have been confirmed in several studies in this area [25–27]. The existing documented reports are given their conclusion in majority that optimization is the only primary, basic and key parameters to improve the enzyme production at maximum extent and is important to analyses and important to monitored at mass scale parameters for industrial usage. Thus, the presented study has provided a new approach to utilize coconut waste and jamun seeds in co-fermentation mode for enhancing maximum enzyme production for economical industrial usage and significant solid waste management.

Fig. 2.

Fig. 2

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Influence of factors on cellulolytic enzymes production, a effect of temperature, b impact of pH, c effect of organic (Y: yeast, P: peptone) and inorganic (NS: Nitrogen Sulphate) nitrogen source

Fig. 3.

Fig. 3

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Effect of moisture content (%) on bacterial cellulase production a FP activity b BGL & EG activity

Conclusion

In order to improve solid state fermentation for cellulase production, co-fermentation of solid wastes and microbial co-cultivation has been emerged as effective strategy to produce high efficient functional enzyme. Under optimum co-fermentative substrate ratio of 5:4 of Ccw and JFs, 16 IU/gds FP activity has been noticed in 12 h of incubation of SSF using bacillus sp. under co-cultivation mode of SSF. Further, at optimum incubation production temperature of 42 °C and pH 6.0, enzyme showed 19 and 21 IU/gds FP activity at 12 h of SSF process. Further, via studying organic and inorganic sources, enzyme produced 26 IU/gds FP activity at 12 h in presence of peptone nitrogen source. In addition, at 60% optimum, moisture content, enzyme gave highest 31 IU/gds FP activity, 239 IU/gds BGL and 176 IU/gds EG activity in 12 h of incubation of SSF. The study has scope in the area of biorefinaries, enzyme industries and solid waste management to produce efficient active raw enzymes at lower cost and in sustainable way.

Acknowledgements

All authors are thankful for their parent institutions. The authors extend their appreciation to the Researchers Supporting Project number (RSP2023R367), King Saud University, Riyadh, Saudi Arabia.

Author contributions

Pathan Ahemad Khan: Writing original draft, editing; Tripti Singh: Writing original draft, editing; Basant Lal: Writing original draft, editing; Rajeev Singh: Writing original draft, editing; Asad Syed: Review, editing; Meenakshi Verma: Review, editing; P. K. Mishra: Supervision, review editing; Ling Shing Wong: Review, editing; Irfan Ahmad: editing and review; Neha Srivastava: Supervision, review editing. The authors are thankful to the Deanship of Research and Graduate Studies, King Khalid University, Abha, Saudi Arabia, for financially supporting this work through the Large Research Group Project under Grant no. R.G.P.2/513/45.

Declarations

Conflict of interest

Authors of the manuscript declare there is no conflict of interests.

Footnotes

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Pathan Ahemad Khan, Tripti Singh, Basant Lal and Rajeev Singh have equally contributed to this work.

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