STUDYING THE GROWTH DYNAMICS OF Lentinus edodes STRAIN IN DIFFERENT NUTRIENT MEDIA AND DETERMINING THE MOST EFFECTIVE MEDIA

ABSTRACT

This article discusses Lentinus edodes, a basidiomycete species with high food and medicinal value, which is one of the organisms widely studied in the fields of modern mycology and biotechnology. It contains biologically active substances such as β-glucans, eritanin, lentinan, which have immunomodulatory, antioxidant, anticarcinogenic and hypocholesterolemic effects, which increase the possibility of their use in the medical and functional food industries. Therefore, the effective propagation of L. edodes mycelium in laboratory and industrial conditions and obtaining its biomass at a high level is an important biotechnological issue.

The relevance of this study is aimed at studying the main factors affecting the development of L. edodes mycelium in local climatic and feed environment conditions. In particular, the physiological requirements, development dynamics and adaptation of this species to feed environments in Central Asia have not yet been sufficiently studied. The study selected the L. edodes strain stored in the Laboratory of Microbiology and Biotechnology of Karshi State University.

In the experiment, the growth rate of mycelium over 7 days was evaluated on various nutrient media - PDA (Potato Dextrose Agar), MEA (Malt Extract Agar), WDA (Wheat Dextrose Agar). The diameter of the colony in Petri dishes was measured every day and the growth rate (mm/day) was determined. All media were incubated under standard sterile conditions at a temperature of 25±1°C.

According to the results, the MEA medium was confirmed to be the most optimal medium for mycelium growth. Within 7 days, the mycelium diameter reached 105 mm, which indicates that it is a medium rich in carbohydrates, trace elements and vitamins due to the malt extract in its composition. Growth in PDA medium was 98 mm, while in WDA medium it was relatively slow - 77 mm. Lag, exponential and stationary phases were clearly observed in mycelial growth.

АННОТАЦИЯ

В данной статье рассматривается Lentinus edodes, вид базидиомицета с высокой пищевой и лекарственной ценностью, который является одним из организмов, широко изучаемых в области современной микологии и биотехнологии. Он содержит биологически активные вещества, такие как β-глюканы, эританин, лентинан, которые обладают иммуномодулирующим, антиоксидантным, антиканцерогенным и гипохолестеринемическим действием, что увеличивает возможность их использования в медицинской и функциональной пищевой промышленности. Поэтому эффективное размножение мицелия L. edodes в лабораторных и промышленных условиях и получение его биомассы на высоком уровне является важной биотехнологической проблемой.

Актуальность данного исследования направлена на изучение основных факторов, влияющих на развитие мицелия L. edodes в местных климатических и кормовых условиях. В частности, физиологические потребности, динамика развития и адаптация этого вида к кормовым средам в Центральной Азии до сих пор недостаточно изучены. Для исследования был выбран штамм L. edodes, хранящийся в лаборатории микробиологии и биотехнологии Каршинского государственного университета.

В ходе эксперимента оценивалась скорость роста мицелия в течение 7 дней на различных питательных средах - PDA (Potato Dextrose Agar), MEA (Malt Extract Agar), WDA (Wheat Dextrose Agar). Диаметр колонии в чашках Петри измерялся каждый день и определялась скорость роста (мм/сутки). Все среды инкубировались в стандартных стерильных условиях при температуре 25±1°C.

По результатам подтверждено, что среда MEA является наиболее оптимальной средой для роста мицелия. В течение 7 дней диаметр мицелия достигал 105 мм, что свидетельствует о том, что это среда, богатая углеводами, микроэлементами и витаминами за счет солодового экстракта в ее составе. Рост на среде PDA составил 98 мм, тогда как на среде WDA он был относительно медленным - 77 мм. В росте мицелия четко наблюдались запаздывающая, экспоненциальная и стационарная фазы.

Kewwords: Lentinus edodes, microbiology, biotechnology, mycelium, strain, fungi.

Ключевые слова: Lentinus edodes, микробиология, биотехнология, мицелий, штамм, грибы.

Introduction

The mushroom Lentinus edodes (shiitake) is of great importance in the field of modern mycology and biotechnology. It is recognized not only as a product of high nutritional value, but also as a source of biologically active substances with immunomodulatory, antioxidant, anticarcinogenic and hypocholesterolemic properties. (Chang & Miles, 2004) [4], (Wasser, 2010) [3]. This basidiomycete is widely used in various fields around the world, especially in the medical and functional food industries.

The effective growth of L. edodes mycelium in laboratory and industrial conditions largely depends on the composition and physicochemical properties of the nutrient medium used. The main factors affecting mycelial development include carbohydrate and nitrogen sources, mineral nutrients, pH, and incubation temperature (Royse, 2014). These factors directly affect the growth rate, morphology, and metabolic activity of the mycelium.  

Potato Dextrose Agar (PDA), Malt Extract Agar (MEA), Wheat Dextrose Agar (WDA), and Synthetic Mushroom Medium (SMM) are widely used for L. edodes (Zhang et al., 2013; Kim et al., 2008).

The effective growth of L. edodes mycelium in laboratory and industrial conditions largely depends on the composition and physicochemical properties of the nutrient medium used. The main factors affecting mycelial development include carbohydrate and nitrogen sources, minerals, pH level and incubation temperature (Royse, 2014) [5]. These factors directly affect the growth rate, morphology and metabolic activity of the mycelium.

For L. edodes, various nutrient media such as Potato Dextrose Agar (PDA), Malt Extract Agar (MEA), Wheat Dextrose Agar (WDA) and Synthetic Mushroom Medium (SMM) are widely used (Zhang et al., 2013) [6], (Kim et al., 2008) [7]. In particular, in studies in India, various strains of L. edodes – DMR-327, Le-18-01 and Le-18-02 – were grown on PDA, MEA, OMA (oat flour), SDA (sawdust), WDA media and their efficiency was evaluated in terms of colony diameter. In these studies, the Le-18-01 strain showed a high growth rate on WDA media (Pilla A.,2022) [8].

In recent years, research has been conducted in Uzbekistan to study the growth characteristics of local macrofungi on nutrient media. In 2021–2022, 17 species of medicinal macrofungi were identified in various regions of Uzbekistan. The study studied their morphological characteristics, molecular phylogeny, preferences, and geographical distribution (Gafforov, 2023) [9]. This information is an important source for the use of medicinal mushrooms in folk and modern medicine. In addition, in 2020–2022, Inonotus hispidus (Sherkulova et al., 2023) [10] and Lentinus tigrinus in 2023 were identified in the Kashkadarya region and their morphological characteristics were studied (Sherkulova et al., 2023 [11], Eshonkulov et al., 2022) [12]. This study aims to study the dynamics of mycelial development of Lentinus edodes strain in various nutrient media (PDA, MEA, WDA, etc.) and to identify the most effective medium among them. The results of the study will serve to improve the technology of effective cultivation of the fungus in laboratory and industrial conditions.Therefore, this study aims to fill this gap.

Research source and methods

A strain of L. edodes maintained in the collection of the Microbiology and Biotechnology Laboratory at Karshi State University was used as the object of this study.

The strain was re-cultivated under sterile conditions and inoculated onto various nutrient media – PDA (Potato Dextrose Agar), MEA (Malt Extract Agar), and WDA (Wheat Dextrose Agar) – to evaluate mycelial growth over a 7-day period. The mycelial diameter, expansion degree and mycelial density surface were measured using a transparent ruler.

All media were incubated in Petri dishes at a temperature of 25±1°C. Mycelial growth was monitored daily, the colony diameter was measured, and the growth rate was calculated [1], [2].

 The composition of the nutrient media:

PDA: 200 g potato juice, 20 g dextrose, 15 g agar-agar, 1 l distilled water, pH ≈ 5.6. MEA: 30–50 g malt extract, 5 g peptone, 15–20 g agar, 1 l distilled water, pH ≈ 5.4 ± 0.2. WDA: 100 g wheat boiled in 500 ml water, 200 ml of water, 20 g dextrose, 15 g agar, 1 l distilled water.

Results and discussion.

According to the results of the study, the L. edodes strain exhibited different growth patterns on various nutrient media (Figure 1). The highest mycelial growth was observed on MEA medium—105 mm within 7 days. During the first two days, growth was relatively slow (7–10 mm/day), but from the third day onward, active development was observed, reaching peak growth rates of 20–22 mm/day on days 5–6. On the 7th day, growth slightly decreased (14 mm), indicating the onset of the stationary phase.

On PDA medium, the mycelium grew to 98 mm over 7 days. Growth was slow during the initial days (8–10 mm/day), but accelerated in the following days (13–21 mm/day).

In contrast, on WDA medium, mycelial growth was relatively slower, reaching 77 mm by day 7. The highest growth rates were observed on days 4–6 (14–16 mm/day), after which growth began to decline.

Figure 1. Seven-day-old cultures of Lentinus edodes: A – on MEA medium, B – on PDA medium, C – on WDA nutrient medium

The results of this study indicate that MEA medium is the most effective for L. edodes. It contains malt extract derived from wheat, which is rich in carbohydrates, vitamins, and trace elements. These nutrients promote rapid mycelial growth and even distribution across the substrate. Additionally, MEA has a neutral to slightly acidic pH (5.5–6.0), which is optimal for the growth of L. edodes mycelium.

Figure 2. Growth chart of L. edodes mycelium

Figure 2 presents a diagram of the 7-day growth rate of L. edodes mycelium on PDA, MEA, and WDA nutrient media, showing daily growth (mm/day) and total growth (mm) measurements.

This graph shows the daily growth rate (mm/day) of Lentinus edodes mycelium on MEA, PDA, and WDA nutrient media.

MEA was found to be the most suitable medium for L. edodes mycelial growth. The highest growth rates on this medium were observed on days 5 and 6, reaching 22 mm/day.

Good growth was also observed on PDA medium, with the growth rate reaching 21 mm/day on day 5. However, after day 6, growth began to slow down, decreasing to 10 mm/day by day 7. On WDA medium, mycelial growth was comparatively slower, with the maximum rate reaching only 15 mm/day on days 5 and 6. Although growth on this medium was stable, it remained consistently slow.

Overall, mycelial growth is rapid during days 1 to 5, while a decline is observed in all media on days 6 and 7.

The results of the present study demonstrated that Lentinus edodes mycelium grows differently depending on the nutrient composition of the medium. The MEA medium showed the highest mycelial growth, which correlates with previous findings by Royse (2014) and Zhang et al. (2013), who also reported that malt extract-based media support rapid fungal development due to their high carbohydrate and vitamin content.

Interestingly, although PDA is traditionally used for fungal growth due to its balanced nutrient profile, it was slightly less effective than MEA in our study. This could be due to the lack of certain trace elements and vitamins present in malt extract. WDA, which was prepared from wheat infusion, demonstrated the lowest growth rate, indicating that while wheat contains some carbohydrates, its nutrient balance may not be optimal for L. edodes.

Our findings are consistent with those reported by Pilla et al. (2022), who observed strain-dependent growth behavior of L. edodes on various nutrient media. In their study, the Le-18-01 strain grew best on WDA, while in our study the local strain showed better adaptation to MEA. This suggests that regional strain differences and substrate composition play a critical role in mycelial growth outcomes.

The observed lag, exponential, and stationary phases of mycelial growth across all media are typical for fungal development and were clearly visible in the growth curves. The accelerated growth on days 3–6 on MEA medium suggests rapid metabolic adaptation, possibly linked to enzyme activation and nutrient assimilation.

One limitation of this study is that only the diameter of the mycelial colony was measured. Future work could include biomass dry weight, enzyme activity, and bioactive compound quantification to provide a more comprehensive picture of fungal productivity on each medium. Additionally, the molecular or transcriptomic analysis of the strain under different media conditions would allow us to understand gene expression patterns influencing growth dynamics.

In conclusion, the study contributes valuable data on the optimization of nutrient media for cultivating Lentinus edodes under local laboratory conditions. These results can support further development of biotechnological applications of medicinal fungi in Uzbekistan and Central Asia.

Conclusion

The results of the study showed that different nutrient media have varying effects on the growth of L. edodes mycelium. The highest growth rate and most effective development were observed on MEA medium, where the mycelial diameter reached 105 mm within 7 days. The rich carbohydrates, vitamins, and trace elements present in the MEA medium contributed to the active growth of the mycelium.

The growth rate on PDA medium was slightly lower compared to MEA, with mycelial growth reaching 98 mm over 7 days. On WDA medium, mycelial growth was noticeably slower, with a total growth of 77 mm recorded over the 7-day period.

This difference highlights the importance of the composition and pH of the medium on mycelial development. During mycelial growth, distinct lag, exponential (active growth), and stationary phases were observed.

These results open up possibilities for the effective propagation of L. edodes mycelium under local conditions and its application for biotechnological purposes. Future studies should focus on investigating the effects of nutrient medium composition on mycelial metabolic activity, enzymatic activity, and the production of biologically active compounds.

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