Rhizopus oligosporus-Assisted Valorization of Coconut Endosperm Waste by Black Soldier Fly Larvae for Simultaneous Protein and Lipid to Biodiesel Production

Abstract

Coconut endosperm waste (CEW) was treated by Rhizopus oligosporus via in situ and ex situ fermentations together with bioconversion into valuable black soldier fly larval biomass. The ex situ fermentation could overall enrich the nutritional compositions of CEW by hydrolyzing its complex organic polymers and exuding assimilable nutrients to enhance the black soldier fly larvae (BSFL) growth. Nevertheless, the larval gut bacteria were competing with Rhizopus oligosporus in in situ fermentation, derailing the hydrolysis processes and larval growth. Accordingly, the highest growth rates achieved were around 0.095 g/day, as opposed to only 0.065 g/day whilst using 0.5 wt% of Rhizopus oligosporus to perform ex situ and in situ fermentations, respectively. These were also underpinned by the greater amount of total CEW consumed when employing ex situ fermentation, with comparable metabolic costs to feeding on in situ-fermented CEW. The mature BSFL were subsequently harvested and the amounts of protein and lipid produced were assessed in terms of their feasibility for biodiesel production. While the statistical analyses showed that the larval protein yields derived from both fermentation modes were insignificant, the BSFL could attain higher lipid and protein productivities upon feeding with ex situ- rather than in situ-fermented CEW mediums. Better yet, the larval biodiesel quality measured in terms of the fatty acid methyl ester composition were not varied significantly by Rhizopus oligosporus through the fermentation process. Thereby, the presence of 1.0 wt% Rhizopus oligosporus was considered optimum to perform ex situ fermentation, giving rise to the acceptable growth of BSFL loaded with the highest lipid yield and productivity for producing biodiesel and protein simultaneously.

Original article: fermented pulp and paper bio-sludge as feed for black soldier fly larvae

“…The content of protein and fat in larvae have not been analyzed in this study. However, previous studies on bioconversion of fermented CEW have reported the following values: protein 15-39% [18,20,22] and fat 44-58% [18,21,22]. Analysis of protein and fat in larvae reared on PPBS is recommended for future studies.…”

“…The bioconversion of the liquid is therefore substantially higher than for the sediment, which illustrates the need for further research on improved fermentation of PPBS. Important fermentation factors not tested in this study are water content [9,[18][19][20][21], process duration [9,19,20], and co-fermentation [33] as well as inoculum concentration [19][20][21][22]. Several methods to improve fermentation of lignocellulose by pre-processing have been reported: physical using microwaves, ultrasound, steam explosion, or heating; biological using microorganisms or fungi (i.e., white root fungi); and chemical using strong acids, alkalis, organic solvents, or ionic liquids [34].…”

“…Lim et al [18] used a mix of self-fermented CEW and soybean curd residue. Wong et al have studied bioconversion of fermented coconut endosperm waste (CEW) in several ways: as fermented ex situ by bacteria [19,20], as fermented in situ by yeast [21], and as fermented by fungi in situ as well as ex situ [22].…”

The effect of pH, temperature, and inoculum on the fermentation of pulp and paper biosludge: increasing the nutrient availability for rearing of black soldier fly larvae

“…[8]. Improving nutrient availability by anaerobic digestion is one method of pretreatment that has been discussed recently [8][9][10][11][12][13][14][15][16]. Disintegration, hydrolysis, acidogenesis (also called fermentation), acetogenesis, and methanogenesis are the steps in anaerobic digestion [17]: large organic compounds are first broken down into monomers, then further converted by microorganisms to volatile fatty acids (VFAs), alcohols, carbon dioxide, hydrogen, and methane [18].…”

Farmed insects for sustainable food systems

“…Unlike the larval transamination pathway, the microbial biomass pathway could reduce manure NH 3 emissions if NH 3 -N assimilation in larvae is maximized via rearing conditions. For instance, substrates inoculated with microbes can increase both bioconversion and larval weights (Mazza et al, 2020;Wong et al, 2021), although this is not always the case (Gold et al, 2021;Hasnol et al, 2020). Future assessments should elucidate if increased bioconversion due to specific microbial inocula is correlated with larger NH 3 -N assimilation in manurebased diets.…”