Optimization of process conditions for tannin content reduction in cassava leaves during solid state fermentation using Saccharomyces cerevisiae

Abstract

Cassava leaves are a crucial source of alternative protein resources for both humans and livestock in developing societies in African and Asian countries that do not have easy access to available protein sources. Hence, cassava has the capacity to promote the economic development of these countries and provide food security. However, it has some disadvantages due to the anti-nutrient compounds present in its tissues, which limits the nutritional value of cassava leaves. Thus, proper processing of cassava leaves is essential in order to reduce the anti-nutrients to a safer limit before utilization. This study focuses on reducing the tannin content of cassava leaves during solid-state fermentation using Saccharomyces cerevisiae . In addition, the Box-Behnken design of the Response Surface Methodology was applied to optimize various process parameters, such as carbon concentration, nitrogen concentration, moisture content, and incubation time for maximum reduction of tannin content in cassava leaves. A quadratic model was developed for the reduction of tannin content, which resulted in a perfect fit of the experimental data (p < 0.01). The optimal conditions were found at 1.4% (w/w) of carbon concentration, 0.55% (w/w) of nitrogen concentration, 57% (v/w) moisture content, and an incubation time of 96 h. The minimum tannin content obtained under these conditions was 0.125%, which indicated a reduction of 89.32 % in tannin content. Conversely, the protein content was increased with a further increase in fermentation time from 24 to 96 h (from 10.08 to 14.11–16.07 %). Furthermore, the ability of Saccharomyces cerevisiae to produce tannase under solid-state fermentation of cassava leaves was also studied. The maximum yield was obtained with an enzyme activity of 0.53 U/gds after 72 h of incubation.

Fermentation of Cereals and Legumes: Impact on Nutritional Constituents and Nutrient Bioavailability

“…Olaleye et al [190] reported an increased nutritional content as well as a significant reduction in oxalate (16.5-68%), phytate (13.7-26%) and tannin (9.2-25.7%), following the fermentation of beans for 72 h at 45 • C with no reported mechanism. As described in various studies, the fermentation of cereals and legumes reduces tannins via hydrolysis by tannase, which catalyses the hydrolysis of ester and depside bonds, yielding gallic acid and glucose [168,207,208]. This enzymic degradation of tannins is facilitated by a lower pH, such as that achieved during the fermentation of legumes and cereals.…”

“…This enzymic degradation of tannins is facilitated by a lower pH, such as that achieved during the fermentation of legumes and cereals. Some researchers have suggested that the reduction in tannins during fermentation may also be attributed to its water solubility; hence, leaching out into the fermenting media, just as all other polyphenolic compounds [207][208][209]. Elsewhere, the fermentation of tamarind seed for 72 h resulted in up to an 85.7% reduction in tannin, 89.4% reduction in trypsin inhibitor activity and 14.3% reduction in phytate [198].…”

Date Seeds Flour Used as Value-Added Ingredient for Wheat Sourdough Bread: An Example of Sustainable Bio-Recycling

“…This is likely attributable to microbial tannases, which release gallic acid from tannins, thus reducing their interaction with proteins and their affinity for iron ( Gänzle, 2020 ). Extracellular and intracellular tannases were previously described in L. plantarum and S. cerevisiae ( Iwamoto et al, 2008 ; Curiel et al, 2009 ; Jiménez et al, 2014 ; Hawashi et al, 2019 ).…”

Cassava Cultivars Response to Different Levels of Potassium Fertilization under Drip Irrigation and Sandy Soil Conditions

“…This crop also has a high nutritional value because it is rich in the content of carotenoids, minerals and vitamin C as well as very high content of starch (800-900 g kg -1 dry weight; Li et al 2017). Cassava leaves are common vegetable among some countries in Africa while the stem is used as planting material during cassava production (Hawashi et al 2019). Cassava plants also have a distinguished list of industrial applications including the medicine, biopolymers, cosmetics food and feed as well as the production of ethanol and biofuel (Adekunle and Raghavan2017;Li et al 2017;James et al 2019).…”

“…The wastes derived-cassava could be used also in the biorefinery and industrial applications (Zhang et al 2016 andde Carvalho et al 2018), which could mitigate the carbon emission and save the energy (Jiang et al 2019). Cassava crop has some problems including the short postharvest shelf-life about 1-3 days (Uchechukwu-Agua et al 2015;Djabou et al 2017), the low protein content and the high content of cyanogenic compounds (Tshala-Katumbay et al 2016), and existence of anti-nutrients in its tissues like tannins, polyphenols andphytic acid (Hawashi et al 2019). Otherwise, this crop may be favor under small-and large-scale cultivation (Li et al 2017).…”