Volume 6 - 2023 - issue 2

1. Analyses of challenges faced during the production of amylolytic enzymes and bio-ethanol using left-over cooked-rice, and rice unfit for human consumption

Authors: Kumar R, Babu P, Vinoth V, Vignesh K, Rani S, Renganathan S, Sarma V

Recieved: 20 August 2022, Accepted: 06 March 2023, Published: 11 August 2023

Rice-based enzyme and alcohol production bio-processes using fungi have been explored for years, but they have suffered from the long-pending predicament of presenting their challenges. Currently, major agricultural countries have been resorting to the usage of surplus first-generation biomass sources in bio-refineries. The present lab-scale work proposes, analyzes, and presents the scale-up challenges of such processes while using a novel mixture of left-over cooked rice and market-rejected rice grains. Fractionated rice grains were used as the substrates for enzyme production. Alpha-amylase (365 IU/mL) was produced by employing Aspergillus oryzae 113 ATCC [9102], while glucoamylase (96 IU/mL) was produced by employing Aspergillus niger A1143 NRRL3 [DSM2466] in separate 144-h-long bio-processes. A mixture of left-over cooked rice and rice grains was sequentially saccharified using the produced enzymes, showing a cumulative 51.66% saccharification. Fermentation of the saccharified hydrolysate using Saccharomyces cerevisiae yielded 59.2 g/L bio-ethanol (starch-conversion: 63.3%) with 190-proof purity (95% v/v). The impact of the enzyme/bio-ethanol production on the coefficients of fungal biomass yield (Yx/s, Yx/O2) and maintenance (msx, mO2x), the rates of specific growth (μ) and substrate uptake (SUR) were analyzed individually. A fundamental techno-economic analysis of the entire process has been presented.

Keywords: Hydrolysate – Fungal biomass yield – Saccharification – Yield and maintenance coefficients – Specific growth rate – Techno-economic analysis.

2. Efficacy of Botanical Mixture and Fungicides to Combat Sigatoka Disease in Banana Cultivation

Authors: Dissanayake M, Herath H, Jayasekara HM, Abeywickrame PD.

Recieved: 22 November 2023, Accepted: 24 May 2023, Published: 18 August 2023

Black Sigatoka disease caused by Mycosphaerella fijiensis seriously threatens banana cultivation worldwide. This infirmity is controlled by the recurrent application of synthetic fungicides, which leads to several adverse effects. Plant extracts with antifungal potential have long been investigated as they contain secondary bioactive compounds for protecting crops from microbial infection. This study compared the antifungal activities of both botanical mixtures and recommended fungicides to control Black Sigatoka in banana. Laboratory and field studies were conducted to assess the antifungal activity of the botanical mix prepared from eight different herbal plant parts against M. fijiensis, with two recommended fungicides as the positive control. In vitro results showed that the radial growth of the fungus was significantly impaired (P<0.05.) by the addition of the botanical mixture, fungicides, and combination of the botanical mixture (BM) and fungicides in the PDA media. Mycosphaerella fijiensis differed in their reaction to the BM and fungicides, and combination of BM and fungicides, but on the whole, growth inhibition increased with the concentration. In field experiments, all the treatments reduced the disease incidence significantly compared to the unsprayed control, where the disease severity index (DSI) increased from 43.88 to 67.77 within 28 days. After the first spray, the botanical mixture and fungicides (Chlorothalonil and Carbendazim) reduced the disease severity index to 39.7, 41.19, and 44.44, respectively. Fungicides and combinations of Chlorothalonil + BM and Carbendazim + BM showed the lowest DSI, 34.07 and 35.83, respectively. The results show that combining the synthetic and botanical mixture is more effective for controlling the disease. The study reveals the possibility of utilizing a botanical mixture as an integrated approach to manage Black Sigatoka disease more efficiently and in an eco-friendly manner.

Keywords: Antifungal Activity – Carbendazim – Chlorothalonil – Mycosphaerella fijiensis – Plant extracts

3. Antioxidant activity and nutritional composition of different mushroom extracts grown on different bush encroachers as substrates in Namibia

Authors: Haukongo KN, Horn LN, Tjiurutue MC

Recieved: 25 April 2023, Accepted: 28 April 2023, Published: 28 September 2023

Mushrooms are a good source of antioxidants with a range of health benefits owing to their bioactive compounds, such as polyphenols, vitamins, and minerals. The objective of this study was to evaluate the antioxidant activity and nutritional composition of mushrooms cultivated on four different encroaching bushes as substrates. Antioxidant activity was measured using reducing power and DPPH scavenging assays. The IC50 values ranged from 0.380±0.098 mg/ml to 0.7780±0.007 mg/ml. The inhibition of the DPPH radical by PS extracts cultivated on Terminalia sericea (0.380±0.098 mg/ml) showed the highest activity compared to other mushroom extracts. All the mushroom species grown on different bushes showed an appreciable ability to reduce ferricyanide complex to ferrous form at different levels of concentration (0.063–1.00 mg/ml). TPC varied from 3.93 mg GAE/g to 8.016 mg GAE/g. TFC ranged from 0.515 mg QE/g to 12.1 mg QE/g, which showed a significant difference in the bush species at a p-value of less than 0.01. There was a significant difference in the interaction of bush substrates and mushroom species on crude protein and ash content at p-values of 0.01 and 0.015, respectively. In the current study, crude protein content ranged from 28.0% to 39.0%, with PF grown on Terminalia sericea having a high protein content. A significant difference in % NDF on mushroom species was found, where a variation was detected in HK35, while PF, PO, and PS showed a similar performance in % NDF. The study showed that ash content ranged from 5.77% to 17.9%. Percentage moisture ranged from 86.0% to 87.5%. A significant difference in mineral composition, with PO showing a high content of potassium (2.292%), PF showing a high content of sodium (0.059%), and PS showing a high content of phosphorus (0.746%) as compared to other mushroom species. Among the four different bushes, Combretum collinum (potassium 2.256%, sodium 0.05%, and phosphorus 0.74%) had the greatest effect on the mineral composition of the different mushrooms cultivated. In conclusion, mushrooms are accessible natural food rich in antioxidants, which may boost the immune system against oxidative damage and can be used as potential sources of therapeutic agents.

Keywords: antioxidants – minerals – therapeutic agents – total flavonoids – total phenolics – oxidative stress