Fresh Sugarcane Juice Research Articles

Structural, optical, luminescent and magnetic properties of Gd2O3 nanoparticles: A comparative study on the effect of different green fuels in the sol–gel synthesis tactics

In this study, five samples of Gd2O3 NPs (size range: 4–33 nm) were synthesized by five different green facile and diverse natural products acting as reducing & stabilizing agents such as: fresh juices of sugarcane, lemon, tomato & orange fruits and citric acid via self combustion sol–gel tactics. Powder X-ray diffraction (PXRD), High resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) and Raman analysis affirmed cubic-C type crystal structure of Gd2O3 NPs prepared using citric acid, lemon juice and sugarcane juice. Mixed cubic and monoclinic phases were observed in Gd2O3 NPs prepared using tomato and orange juices. Notably, NPs of Gd2O3 in quantum dot regime (size: 6 ± 2 nm) were produced in the fresh sugarcane juice mediated synthesis protocol. Fresh lemon juice and sugarcane juice were appeared to be the most efficient green fuel for producing quality samples of Gd2O3 NPs. Optical absorption studies showed that bandgap in these Gd2O3 NPs is strongly dependent on the preparation protocol and type of green fuel. Interestingly, highest and lowest band gap of 4.91 eV and 4.43 eV were obtained for Gd2O3 NPs fabricated with orange and lemon juices, respectively. Photoluminescence (PL) and electron spin resonance (ESR) analysis affirmed formation of Schottky and Frenkel surface defects along with self trapped excitons and oxygen vacancies in these Gd2O3 NPs. Paramagnetic character of these Gd2O3 NPs at 300 K is validated by dc-magnetization and ESR studies. Present study demonstrated that microstructural, optical absorption and photoluminescence properties of Gd2O3 NPs can be easily customized by choice of natural products in the synthesis tactics.

Calculation of productive capacity: From theory to practice

This article suggests and conceptualizes a methodology for calculating capacity in production processes, applicable to both the manufacturing industry and service companies. Its relevance lies in the fact that a correct dimensioning of the productive capacities of a company is a fundamental aspect, not only for its operations department, but also for the rest of the functional areas of the organization. The study begins with a reflection of the main concepts associated with measuring the capacity of production processes; where the main activities of the methodology stand out: description of the process, time study, capacity calculation and planning; in addition to the concepts of bottleneck and profitability. And it ends with the application of the step-by-step methodology on a case raised about a venture about the sale of fresh sugar cane juice on weekends at a farmer market. In short, it is important to mention that the article also aims to serve as a tool to contribute to the development of the Know-How competencies of future industrial engineers given its importance recognized by the employers sector (Ramírez-Mora, 2023). And, that it serves as an instrument to facilitate the study of students during their hours of independent work in their study plans. (Ramírez-Mora, 2023).

Membrane assisted Pulsed Electric Field (M-PEF) a novel technique for preservation of functional and biological properties of sugarcane juice.

Abstract According to market prospects there is a demand for the bottled fresh sugarcane juice than any other fruit based beverages because of its nutritional and therapeutic properties. Sugarcane juice short shelf life and deterioration are linked to the existence of active enzymes like peroxidase and polyphenol oxidase as well as its microbial composition. The membrane assisted pulsed electric field technology (M-PEF) was used for this experiment in which the hollow spiral wound ultra-filter membrane for 10 kDa pore size at 1 bar pressure employed as a pretreatment to pulsed electric field processing for the treatment of sugarcane juice. The process parameters are 20, 30, and 40 kV/cm field strength for the pulse width of 100, 150, and 200 μs. The reduction of 92% in polyphenol oxidase and 80% in peroxidase enzyme activity was achieved due to Pulsed electric field at a field strength and pulse width of 30 kV/cm for 150μs respectively retaining the overall quality of the sugarcane juice and there was 85-95% reduction was observed in the protein and polysaccharide content of the sugarcane juice due to the membrane filtration pore size exclusion effect. Ascorbic acid content was retained in the M-PEF samples while increasing its antioxidant capacity. The experiment results showed that due to Pulsed electric field treatment there was 3 log reductions are observed on total plate count. This technology showed that, it can be used as novel technique for the preservation of the fresh juices.

Sugarcane Consumption and its Multifaceted Impact on Physiological Parameters: Exploring Associations with Blood Pressure, Blood Glucose Levels, Body Temperature, Breathing Rate, and Urinary Characteristics

Background: Sugarcane, a significant agricultural crop, is rich in sucrose, vitamins, and minerals, contributing to nutritional intake. However, the impact of sugarcane consumption on physiological parameters is limited, with previous studies focusing on refined sugar and sugary beverages, leaving a research gap in understanding the specific health effects of sugarcane consumption. The study investigates the impact of sugarcane consumption on various biological parameters, including blood pressure, sugar levels, body temperature, breathing rate, and urine characteristics. Methods: A study involved 200 adult volunteers without pre-existing medical conditions. The participants were divided into two groups: the experimental group, who consumed 250ml of fresh sugarcane juice daily for eight weeks, and the control group, who maintained their regular diet without sugarcane. Blood pressure, glucose levels, body temperature, breathing rate, and urinary characteristics were assessed at baseline and four-week intervals. Data were analyzed using paired t-tests, M-tests, and independent t-tests, and multivariate regression analysis to assess the relationship between sugarcane consumption and physiological parameters. Results: The experimental group exhibited a significant decrease in both systolic and diastolic blood pressure compared to the control group (p < 0.05). Blood glucose levels also showed a modest but statistically significant reduction in the experimental group (p<0.05). No significant differences were observed in body temperature, breathing rate, or urinary characteristics between the two groups. Conclusion: Sugarcane juice consumption in healthy adults showed positive effects on blood pressure and glucose levels over eight weeks, suggesting potential health benefits in managing blood pressure and glycemic control, but further research is needed.

Microbial Quality Assessment of Fresh Sugarcane Juice in Retail Shops Inside Kathmandu Valley

This study aims to assess the microbial quality of fresh sugarcane juice sold in retail shops inside Kathmandu Valley, as there is limited information available on the safety of popular fresh juices like sugarcane juice, which can cause food-borne illnesses when improperly prepared, despite the known health benefits of consuming fresh fruits juices. Sixty fresh sugar cane juice samples were collected from selected thirteen areas inside Kathmandu Valley. Out of 60 samples, 42 samples were contaminated with bacteria. The quality of each sample was assessed by total plate count, total coliform count, yeast and mold count, and isolation of pathogenic bacteria. The isolated bacteria were identified based on biochemical characteristics. The pH of collected samples ranged from 4.33 to 6.34, acidity from 0.01% to 0.09%, and total soluble solids from 13 to 21⁰Brix. The mean bacterial count was 5.26 log10 CFU/ml, the coliform count was 4.67 log10 CFU/ml, and the yeast mold count was 4.94 log10 CFU/ml. E. coli was present in 38.1%, Citrobacter freundii in 47.6%, and Salmonella species in 14.3% of the total sample. Vibrio cholerae was not detected. Gentamicin, Ciprofloxacin, and Ofloxacin were effective, while Ampicillin was less effective. The study found that sugarcane juice samples from shops in Kathmandu Valley have high levels of contamination, including a high microbial load and slightly acidic pH with high total soluble solid values. The bacterial isolates exhibited varied degrees of antimicrobial susceptibilities and resistances, and the contamination was attributed to poor hygienic conditions during juice processing and handling, possibly due to the use of poor-quality water and a lack of training on food hygiene and safety. These findings suggest potential health hazards for consumers of fresh sugarcane juice.

Influence of low temperature hydrodynamic cavitation treatment on shelf life of ascorbic acid‐treated sugarcane juice

AbstractSugarcane juice has a lower shelf life owing to enzymatic browning as well as microbial activity. To overcome these issues, fresh sugarcane juice was treated with ascorbic acid, a strong antioxidant, and further subjected to low‐temperature hydrodynamic cavitation (LTHC) treatment at 4°C/.35 MPa for 30 min. The AALHC‐treated juice was filled into PET bottles and stored under atmospheric (25 ± 5°C) and refrigerated (4 ± 1°C) conditions. The changes in reducing sugar, total sugar, color (ΔE), microbial load, total phenolic content, total flavonoid content, and antioxidant activity of sugarcane juice during the storage period were evaluated. During the storage, better retention of the quality parameters was observed in the AALTHC processed sugarcane juice followed by AA‐treated sugarcane juice and fresh sugarcane juice. Under the atmospheric storage, fresh juice and AA‐treated juice were spoiled within a day, whereas the AALTHC‐treated sugarcane juice could last for 4 days. On the other hand, under the refrigerated storage conditions (4 ± 1°C), the quality of the fresh and AA‐treated sugarcane juice could last only for a week, while the quality of AALTHC could be maintained up to 42 days.Practical ApplicationsThe current study aims to improve the shelf life of sugarcane juice by low‐temperature orifice‐based hydrodynamic cavitation. Sugarcane juice has a short shelf life owing to high levels of microbiological contamination and enzymatic reactions that begin immediately following extraction. The use of hydrodynamic cavitation technique enables a significant reduction in microbial load as well as spoilage enzymes, with minimum effect on the nutrient profile and sensory qualities. The treatments presented in this study are successful, inexpensive, more practicable, and long‐term enough to be scaled up for larger‐scale production of sugar cane juice. The outcomes of this study may be useful for developing a fortified beverage industry employing low‐temperature hydrodynamic cavitation.

Preparation, production and characteristics of sugarcane vinegar

Sugarcane is one of the main crops worldwide, and it has an important impact on environmental issues. Sugarcane is used in daily routine life in many ways like as vinegar, jiggery, juices etc. In India sugarcane crop is best cultivated in the west U.P. Sugarcane original vinegar drink with high nutritional quality was produced from fresh sugarcane juice using the yeast culture and acetic acid bacteria by fermentation techniques such as submerged alcoholic fermentation followed by acetic fermentation at room temperature. Refined sugarcane is the primary product of sugarcane juice, during its processing, various other valuable products are also obtained in an unrefined form such as brown sugar, molasses, jaggery and vinegar. Sugarcane juice is widely used in the treatment of jaundice, hemorrhage, dysuria, and other urinary disease. Nowadays sugarcane vinegar is also used in Indian kitchens commonly in pickles, salads, etc. Vinegar is extremely useful for human health including antimicrobial activity, blood pressure reduction, antioxidant activity, reduction in the effects of diabetes, and prevention of cardiovascular disease. Phenolic acid in vinegar can scavenge superoxide anion and free radicals in vivo resulting in a potent antioxidant activity.

Vinegar: A potential source of healthy and functional food with special reference to sugarcane vinegar.

Vinegar is one of the most widely used acidic condiments. Recently, rapid advances have been made in the area of vinegar research. Different types of traditional vinegar are available around the globe and have many applications. Vinegar can be made either naturally, through alcoholic and then acetic acid fermentation, or artificially, in laboratories. Vinegar is the product of acetic acid fermentation of dilute alcoholic solutions, manufactured by a two-step process. The first step is the production of ethanol from a carbohydrate source such as glucose, which is carried out by yeasts. The second step is the oxidation of ethanol to acetic acid, which is carried out by acetic acid bacteria. Acetic acid bacteria are not only producers of certain foods and drinks, such as vinegar, but they can also spoil other products such as wine, beer, soft drinks, and fruits. Various renewable substrates are used for the efficient biological production of acetic acid, including agro and food, dairy, and kitchen wastes. Numerous reports on the health advantages associated with vinegar ingredients have been presented. Fresh sugarcane juice was fermented with wine yeast and LB acetate bacteria to develop a high-quality original sugarcane vinegar beverage. To facilitate the current study, the bibliometric analysis method was adopted to visualize the knowledge map of vinegar research based on literature data. The present review article will help scientists discern the dynamic era of vinegar research and highlight areas for future research.

Different Treatments for Sugarcane Juice Preservation.

This investigation aimed to optimize the time, pH, pressure, and temperature of sugarcane juice pasteurization and to develop a "ready to serve" bottled sugarcane juice with a high preservation efficiency. Fresh sugarcane juice was extracted from sugarcane genotype Co 89003, and beverage samples were collected using three different treatments: sulphitation of juice with the addition of potassium metabisulphite (KMS-25, 50, 100, and 150 ppm), acidification of juice (addition of citric acid, to reduce the pH of the juice to 4.8, 4.5, and 4.25), and steam treatment of the canes (5 min, 10, and 15 min at 7 psi). In all treatments, the juice was pasteurized in glass bottles @ 65 °C for 25 min and stored at low temperature (5 °C) in pre-sterilized glass bottles. Juice properties such as the ˚Brix, total sugar, pH, and total phenolic content decreased with storage, whereas the microbial count, titrable acidity, and reducing sugar content significantly increased during storage. The addition of KMS, citric acid, and the steam treatment reduced the browning of juice and maintained the color of juice during storage, by inhibiting the polyphenol oxidase enzyme activity, from 0.571 unit/mL to 0.1 unit/mL. Among the selected treatments, sugarcane juice with KMS (100 and 150 ppm) and steam treatment of the canes for 5 and 10 min at 7 psi showed the minimum changes in physico-chemical properties, sensory qualities, and restricted microbial growth. Thesulphitation treatment with pasteurization proved best for increasing the shelf life of sugarcane juice upto 90 days with refrigeration. Similarly, the steam-subjected cane juice (10 and 15 min at 7 psi) could be effectively preserved for upto 30 days with refrigeration, without any preservative.

Sugarcane blanching at specific temperature and time combination preserves juice physio‐biochemical, microbial and sensory attributes

SummaryFresh sugarcane juice packed with sugars, minerals, phytonutrients, antioxidants and proteins is vulnerable to quality losses caused by enzymatic inversion, chemical interactions and microbiological intrusions. Three temperatures (70, 80 and 90 °C) and four time interval combinations (5, 10, 15 and 20 min) were used to thermally blanch sugarcane billets for comparing the effects on physio‐biochemical, microbiological and sensory properties of juice recovered. The optimum and acceptable combination determined was 90 °C for 10 min. The physio‐biochemical parameters vis a vis pH (5.03), titratable acidity (0.198%), electrical conductivity (4.77 mScm−1), total soluble solids (20.67°B), sucrose (18.19%), reducing sugar (0.38%), total plate count (4.42 cfu ml−1), residual PPO activity (12.21%) and colour (L*, b*, chroma) along with sensory profile was most acceptable. A 9‐point hedonic ratings of blanched SCJ retained appearance (9), taste (9), aroma (8.8) and quantitative descriptive analysis showed a close resemblance with fresh sugarcane juice.

Coloration mechanisms of fresh sugarcane juice: Investigating the critical components and enzyme activity.

The color of sugarcane juice has a great influence on the preferences of consumers. The contents of pigments, sugars, free amino acids, organic acids, phenolic compounds, enzyme activities, antioxidant activities, and color differences among juices produced from four sugarcane varieties were investigated in this study. The data suggested that variety played an important role in the color and chemicophysical properties of sugarcane juice. The color of four varieties of sugarcane juice varied from greenish yellow to light brown. Bamboo cane juice and black rind sugarcane juice presented similar color properties and both had high contents of phenolic compounds and strong antioxidant activities. Yellow rind sugarcane juice with higher value of L* (26.10) and more pigment contents than the other varieties was attractive. Sucrose, glucose, β-alanine, chlorogenic acid, p-hydroxybenzoic acid, isochlorogenic acid, DPPH, and polyphenol oxidase activity had positive correlations with a* value. The effects of organic acids on color were limited. PRACTICAL APPLICATION: This study demonstrated the relationships between color parameters and contents of pigments, sugars, free amino acids, organic acids, phenolics, enzyme activities, and antioxidant activities of sugarcane juice. This could help to find out the coloration mechanisms of sugarcane juice. Our manuscript created a paradigm for future studies on color control during juice processing and storage.

Technological upgradations in jaggery making plants

Jaggery, an unrefined sweetener is prepared by continuous heating of fresh sugarcane juice in different types and capacities of old indigenous and modified plants. The old indigenous plants manufactured by the rural people without any technological advancements have very high fuel consumption (about 3 kg/kg to 4 kg/kg of jaggery produced) and low heat utilization efficiency (15% to 29%). Number of modifications have been suggested by the researchers for the optimization and improvement in the performance parameters of jaggery making processes and plants. The implementation of fins at the external bottom of pans, preheater and economiser in the chimney, efficiency booster in the furnace, freeze pre-concentration system, forced draft through the plant and controlled fuel feeding in the furnace are reported to improve the thermal efficiency in the range of 25% to 50% and reduce the bagasse consumption in the range of 1.75 kg/kg to 2.75 kg/kg of jaggery prepared. The recently published article adopting novel techniques of internal preheating of sugarcane juice in the gutter pan and automatic supply of bagasse in the furnace of a two pan jaggery making plant is claimed to improve the heat utilization efficiency up to 65% and reduce the fuel consumption up to 1.50 kg/kg of jaggery produced with an affordable investment. The present paper summarizes the various technological up-gradations adopted and tested by the researchers for the enhancement of various output parameters of jaggery making units.

Orifice based hydrodynamic cavitation of sugarcane juice: Changes in Physico-chemical parameters and Microbiological load

An orifice based hydrodynamic cavitation system was developed for treating fresh sugarcane juice, non-thermally. The effect of hydrodynamic cavitation treatment parameters such as pressure (2.5, 3, and 3.5 bar), processing time (10, 20, 30, 40 min), and type of orifice plate geometry on the physicochemical attributes such as temperature rise, pH, titratable acidity (TA), total soluble solids (TSS), viscosity, change in colour and microbial load of the sugarcane juice were investigated. The maximum rise in temperature during the treatment was 22 °C at 3.5 bars with the 17 number of orifices. The pH decreased from 4.94 to 4.64 and TSS significantly reduced (p < 0.01) from 20 to 13 °Brix depending on the severity of the treatment. The reduction in viscosity was in the range of 3–48%. The maximum colour change in the juice could be observed when treated at an inlet pressure of 3.5 bar for a processing time of 40 min with a plate having 17 numbers of orifices. The maximum microbial load inactivation from 5.53 log10 CFU/mL to 3.3 log10 CFU/mL was observed at the highest pressure, processing time, and orifices.

Phenolic profile of sugarcane juice: Effects of harvest season and processing by ohmic heating and ultrasound

In the present work, a comprehensive phenolic analysis of fresh sugarcane juice from three different harvest seasons was performed and the effect of ohmic heating and ultrasound treatments on the phenolic content and color of the juice was evaluated. Among the 32 phenolic compounds identified, a total of 17 were quantified, comprising, in decreasing order of abundance, flavones (38–49 mg/L), dilignols (22–29 mg/L), and phenolic acid derivatives (17–30 mg/L). The main phenolic groups affected by the crop season (year and season) were flavones and phenolic acid derivatives. Juice treated by ohmic heating and ultrasound showed a total phenolic content similar to fresh juice, indicating the absence of additional non-thermal effects. Regarding color, both treatments promoted only a slight difference by visual perception. Considering these two quality parameters, ultrasound and ohmic heating seem to be a good alternative for sugarcane juice pasteurization.

Influence of ohmic heating on commercial peroxidase and sugarcane juice peroxidase inactivation

Different fractions of sugarcane juice (liquid, solid and concentrated) were ohmically (75 °C and 7.8 V/cm for 25 min) treated to investigate the effect of different sample compounds on peroxidase inactivation. Moreover, commercial peroxidase solutions with and without the addition of sucrose were evaluated during ohmic (OH) and conventional heating (CH – with the same parameters of OH but without electric field application). It was observed that samples ohmically treated presented greater enzymatic inactivation (78% in the liquid fraction and 100% in the solid fraction, after 25 min of treatment) than those treated by CH (72% and 95% for liquid and solid fraction, respectively). The solid fraction was the most labile, and the liquid the most resistant fraction during both heating treatments. The concentrated fraction, which contains all isozymes, presented an intermediate inactivation rate. A zymogram showed three POD isozymes in the fresh sugarcane juice, explaining the different stabilities of the assayed fractions. Furthermore, the presence of sugar promoted a stabilizing effect on enzyme structure when exposed to the electric field, delaying its denaturation.

Explorasi Mikroba Beraroma dari Bahan Alam

Abstract: The Scented volatile compound has a huge market as its wide applications in daily life. The extraction of this compound from natural resources produces a very low rendement. Microbes synthesize secondary metabolit might resemble of their host have been explored from scented natural resources (flowers: Damask rose, Jasminum sambac and Plumeria acutifolia); cymbopogon, muntinga calabura L and leave of Panadus amaryllis). It was found 12 bacterial and 14 fungal scented isolates that were various in terms of scent types and intensities. They were bread starters like the smell, alcohol like the smell, sweet sugar like the smell, salaka like the smell and fresh sugarcane juice like smell. Several isolates emit original host like the smell in very low intensities. Persistency scent test showed that the scents were persistently emitted when cultured on PDA medium. Key Words: Scented volatile; Damask rose; microba; exsplorasi

Physicochemical, Antioxidant and Microbial Properties of Fresh Black Stem Sugarcane Juice with Addition of Calamansi Juice

This study was designed to determine the physicochemical, antioxidant and microbial properties of fresh sugarcane juice with calamansi juice addition. The sugarcane that was used in the experiments was the black cane variety (Saccharum officinarum). Sugarcane pressed with and without their peel was juiced and added with calamansi juice before analysis was carried out. Standard method was used to analyse physicochemical properties such as pH, total soluble solids, acidity and colour of sugarcane juice. Total phenolic content (TPC), DPPH and FRAP assay were conducted for antioxidant properties. Total plate count and yeast and mould count were carried out for the microbiological analyses. Two way analysis of variance (ANOVA) shows significant (p 0.05) difference shown for pH, acidity and total soluble solids of sugarcane juice pressed with and without peel. Sugarcane juice pressed with peel produced higher antioxidant value compared to sugarcane pressed without peel. However, sugarcane juice pressed without peeled showed a lower microbial count compared to sugarcane juice pressed with peel. The addition of calamansi juice proved to have significant (p<0.05) effect on colour, antioxidant and microbial count of the sugarcane juices.

Optimization of process parameter combinations for pasteurization of sugarcane (Saccharum officinarum) juice using continuous flow microwave system

Colour (L*, a*, b*) values of fresh sugarcane (Saccharum officinarum L.) juice added with citric acid, thermal pasteurized and microwave pasteurized juices were significantly higher from that of fresh sugarcane juice. There was no significant difference in TSS and pH values of any of the pasteurized sugarcane juice. PPO activity and total viable bacterial count decreased significantly after thermal and microwave pasteurization of juice whereas yeast was completely eliminated from all the microwave pasteurized and thermal pasteurized sugarcane juices. There was a significant decrease in total antioxidant values after thermal and microwave pasteurization.

PULSED ELECTRIC FIELD FOR PASTEURIZATION OF FRESH SUGARCANE JUICE

Pasteurization methods using pulsed electric fields (PEFs) have proved efficient at non-thermal inactivation of microorganisms and pathogens. The methods usually use a series of high intensity, narrow band electric fields that pass through target mediums where they induce irreversible damage to cellular membranes leading to the death of microorganisms by internal content loss breakage of cell homeostasis and other effects. This research proposed a simple, lab-scale PEF pasteurization equipment that uses common output electric voltages (220V and 110V, which provide electric power of 5.5 and 2.75 kV/m, respectively) with a simple designed Human-Machine Interface control. At a voltage of 110V, the equipment was tested with non-sterilized Czapek medium which showed more than 1.42-log reduction in the microbial density at 30s of the treatment and temperature below 60 o C. A test on suspended E. coli in modified Czapek medium also indicated an inactivation of most of bacterial cells after 40s of the treatment. We then applied the equipment to pasteurize fresh sugarcane juice and, as a result, the content of native microorganisms in sugarcane juice was reduced 1.2-log cycle, compared to that of original juice before the treatment.

High pressure, temperature and time-dependent effects on enzymatic and microbial properties of fresh sugarcane juice.

Efficacy of variable high pressure, temperature and time on the browning causing enzymes and microbial activities, which are major spoilage factors during preservation of sugarcane juice, was studied. The juice was processed at 200-600MPa pressure for 2-8min at 40 and 60°C and their effect on polyphenol oxidase and peroxidase as well as microbiological quality in terms of total plate count, yeast and molds and total coliforms was studied. Application of high pressures were found to cause significant decrease in enzymatic and microbial activities. The effects were found to be significantly more pronounced at 60°C as compared to 40°C. Process time also caused significant (p<0.05) negative effect on microbial and enzyme activities. The sugarcane juice treated at 600MPa for 6min at 60°C was found sufficient to inactivate the microbial counts completely. Whereas, enzymes were found to be completely inactivated in the samples processed at 600MPa for 8min at 60°C. A pressure of 600MPa at 60°C for 8min could be applied during commercial preservation of sugarcane juice for getting complete inactivation of browning causing enzymes and spoilage causing microorganisms.