All Research Publications by bona fide staff of Meru University of Science and Technology http://repository.must.ac.ke/handle/123456789/11 2026-04-09T11:45:43Z 2026-04-09T11:45:43Z Lv, Chenglong Yang, Qin Mariga, Alfred Mugambi Pei, Fei Fang, Yong Xia, Ji http://repository.must.ac.ke/handle/123456789/1582 2026-02-24T13:10:04Z 2025-07-01T00:00:00Z

Isolation, structural characterization and bioactivity of a novel exopolysaccharide from lactic acid bacteria in kefir grains Lv, Chenglong; Yang, Qin; Mariga, Alfred Mugambi; Pei, Fei; Fang, Yong; Xia, Ji Exopolysaccharides (EPS) are important metabolites produced by lactic acid bacteria (LAB), exhibiting diverse biological activities. However, their application is limited by low production levels. This study aimed to isolate, characterize, and evaluate the bioactivities of an EPS (EPS-PAD) from high-yield LAB in kefir grains. A novel EPS-PAD was isolated, purified and analyzed using molecular weight determination, monosaccharide composition analysis, nuclear magnetic resonance (NMR), and methylation analysis. Moreover, the antioxidant activity and anti-inflammatory activity of EPS-PAD were investigated as well. The results showed that EPS-PAD had a relatively low molecular weight (42.7 kDa) and consisted of arabinose, glucose, and galactose (molar ratio 1:1:3). Furthermore, structural analysis indicated it possessed an α-pyranose configuration with branched chain residues. Remarkably, EPS-PAD exhibited potent radical scavenging activities, with rates of 62 % (1,1-diphenyl-2-picrylhydrazyl radicals), 64 % (2,2′-azinobis (3-ethlybenzothiazoline)-6-sulfonic acid radicals), and 76 % (hydroxyl radical). In addition, at 400 μg/mL, EPS-PAD significantly suppressed the production and mRNA expression of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) and upregulated the production of anti-inflammatory cytokine IL-10 in RAW264.7 cells. These findings provide a scientific basis for EPS-PAD from kefir grain LAB as a promising natural antioxidant and anti-inflammatory agent with significant application potential.

2025-07-01T00:00:00Z Du, Weiwei Liu, Jianhui Wanga, Xinhui Sua, Anxiang Xua, Hui Xiea, Minhao Hua, Qiuhui Mariga, Alfred Mugambi Yang, Wenjian http://repository.must.ac.ke/handle/123456789/1581 2026-02-17T16:17:19Z 2025-06-01T00:00:00Z

Edible Fungi-Derived Peptides as Future Food Source: Preparation,Functional Implications, and Perspectives Du, Weiwei; Liu, Jianhui; Wanga, Xinhui; Sua, Anxiang; Xua, Hui; Xiea, Minhao; Hua, Qiuhui; Mariga, Alfred Mugambi; Yang, Wenjian Edible fungi are increasingly regarded as ideal future food source for alternative protein and nutrients. Their bioactive components have been widely recognized for promoting human health and preventing diseases. Among these components, edible fungi active peptides can be obtained from almost any part of edible fungi. This review summarizes current approaches to exact and separate these peptides with the goal of identifying greener and more efficient technologies. In addition to flavor enhancement, fungal peptides can reduce or replace the use of sodium in people’s daily life, thereby contributing to a healthier dietary habit. They also play effectiveness through their regulation of signal pathways and cellular metabolic genes, making them useful as drugs or supplements in both therapy and daily nutrition. Therefore, this review highlights recent advances in peptides from edible fungi, with a focus on their abundant functional activities (e.g. immunity regulation, antitumor, antioxidant and flavor properties) and the underlying mechanisms behind these effects. Importantly, this review is among the first to analyze their potential toxicity. Given their efficiency, sustainability, and nutritional profile, the peptides from edible fungi will have great development and utilization value in the future.

2025-06-01T00:00:00Z Shang, Xueli Tong, Wenying Bai, Shiqi Zhou, Liyao Mariga, Alfred Mugambi Ma, Ning Fang, Donglu Yang, Wenjian Hu, Qiuhui Pei, Fei http://repository.must.ac.ke/handle/123456789/1580 2026-02-17T15:59:40Z 2025-12-01T00:00:00Z

Elevated CO2 maintains cellular integrity and ROS homeostasis in postharvest Agaricus bisporus by regulating energy metabolism and Ca2+ signaling Shang, Xueli; Tong, Wenying; Bai, Shiqi; Zhou, Liyao; Mariga, Alfred Mugambi; Ma, Ning; Fang, Donglu; Yang, Wenjian; Hu, Qiuhui; Pei, Fei Agaricus bisporus (A. bisporus) is highly susceptible to postharvest quality deterioration, including enzymatic browning, cap opening, water loss, and tissue softening. Carbon dioxide (CO2) modified atmosphere packaging is effective in maintaining storage stability of post-harvest edible mushrooms. This study aimed to explore the mechanism by which 6 % CO2 modified atmosphere packaging maintains the postharvest quality of A. bisporus. Postharvest A. bisporus were treated with 6 %, 12 %, 18 % CO2 or air (CK), and stored at 4°C for 18 days. Results showed that 6 % CO2 significantly delayed quality deterioration by coordinating energy metabolism and Ca2+ signaling. Specifically, the treatment enhanced mitochondrial respiratory chain activity, increasing ATP content and energy charge (EC), thereby sustaining the energy supply of postharvest A. bisporus. Meanwhile, 6 % CO2 upregulated antioxidant enzymes, thereby suppressing reactive oxygen species (ROS) accumulation and reducing lipid peroxidation. In addition, it maintained cellular architecture by inhibiting phospholipase and cell wall hydrolase activities. Furthermore, 6 % CO2 elevated cytosolic Ca2+ levels and calmodulin (CaM) content in A. bisporus, while upregulating CML and CaMK expression. This activated Ca2+/CaM/CaMK pathway modulates cell membrane and cell wall metabolism by enhancing ROS scavenging capacity. The pathway likely also coordinates cellular energy homeostasis through downstream signaling. Collectively, these results indicate that 6 % CO2 delays postharvest quality deterioration of A. bisporus via the synergistic regulation of energy metabolism and calcium signaling, providing a mechanistic framework for understanding postharvest quality management of this species.

2025-12-01T00:00:00Z Bai, Shiqi Tong, Wenying Shang, Xueli Mariga, Alfred Mugambi Ma, Ning Fang, Donglu Yang, Wenjian Hu, Qiuhui Pei, Fei http://repository.must.ac.ke/handle/123456789/1579 2026-02-17T15:37:23Z 2026-01-01T00:00:00Z

Transcriptomics reveals the mechanism by which UV-B radiation delays postharvest browning of Agaricus bisporus by maintaining cell membrane stability Bai, Shiqi; Tong, Wenying; Shang, Xueli; Mariga, Alfred Mugambi; Ma, Ning; Fang, Donglu; Yang, Wenjian; Hu, Qiuhui; Pei, Fei Maintaining cell membrane homeostasis is crucial for suppressing postharvest browning in Agaricus bisporus (A.bisporus). This study utilized transcriptomics to investigate the effects of 50 kJ m⁻² ultraviolet B (UV-B) irradiation on cellular membrane homeostasis and metabolic pathways in post-harvest A.bisporus. Results found that 50 kJ m−2 UV-B irradiation treatment effectively attenuated cellular deformation and cytoplasmic leakage by suppressing membrane lipid peroxidation and regulating membrane permeability. The activities of polyphenol oxidase (PPO), tyrosinase (TYR), and laccase (LAC) were reduced by 18.66 %, 27.75 %, and 15.27 %, respectively, compared with the control group, accompanied by the downregulation of the corresponding genes expression levels. The differential expressed genes (DEGs) were mainly clustered in the pathways of fatty acid metabolism, phospholipid metabolism, tryptophan metabolism, and glutathione metabolism. These findings demonstrate that UV-B irradiation treatment delays browning through dual regulation of membrane integrity maintenance and browning-related metabolic suppression.

2026-01-01T00:00:00Z